This is about returning a cart to a corral to prevent it from possibly damaging other cars, taking up space, making the employee waste time gathering them etc.
I leave my cart where the possibility of damaging a car (not just "other cars") is negligible and where it will not get in anyone's way. That leaves "making [an] employee waste time gathering" the carts as the only reason to use the corral. What else is that employee going to do? Retrieving carts from the parking lot is pretty much the only thing that employee has to do. Why should I do that employee's job? Moreover, since I'm not even close to the only person who doesn't generally use the corrals, I don't think changing my behavior is going to have a significant impact on how the cart retrieval employee spends his/her day.
You getting in and efficiently grabbing your food without going into other aisles isn't even the same kind of situation and has nothing to do with laziness because you get nothing out of going into every aisle.
Likewise, I get nothing out of returning carts to he corral. On the other hand, I do lose time. Granted, it's not any significant amount of time, but I view my time as valuable and not to be wasted on things I don't enjoy or which serve no useful purpose.
For each situation:
1) cart in the corral; best option.
2) cart not in corral, left somewhere else; makes employee waste more time gathering them, cart potentially could become loose or even stolen, which is lost property for the store
3) cart blocks a parking space; we agree that is not okay.
So best option? Put it back... be a courteous individual... take a few extra seconds...
I understand your opinion. However, I don't agree with the negatives associated with #2, so I don't see how using the corral is any better.
Who else can be impacted? Courtesy clerks: They don't care and expect as part of their job to get the carts. So courtesy clerks: not negatively impacted.
Not only that, if I do their job for them, they may find themselves out of jobs. Using the cart corral costs people their jobs, damnit!
Wow. Okay, so, the excuse is simply laziness, if it's really not a big deal then. Cool, we agree on that. 
Two things here: (1) If it's "lazy" not to use the cart corral, then it's equally lazy to use the cart corral instead of taking the cart
back where you got it in the first place; and (2) not doing something that serves no useful purpose and refraining from which causes no harm is not "lazy."
I literally work at a body shop where people's cars come in and get fixed for damage like that. If you're arguing that nobody here is impacted by you leaving a cart out, yes, that is correct, but what is the point then? That doesn't refute the argument that it's not courteous to others around you.
No one here is saying that folks who let carts roam free to maim and kill innocent cars isn't a problem.
And since you seem to be bothered by the Mexican analogy, although I can't fathom why, here's maybe a better one, although fictitious:
Person A takes meticulous care of his lawn, and doesn't like anyone on it, period. He makes that known, and everybody who lives near him knows it. He's a good guy. He just doesn't like people on his lawn.
Person B takes meticulous care of his lawn because he likes the way it looks when he does, but he doesn't really care one way or the other whether people walk on it or not, as long as they are reasonably careful not to tear it up. Yeah, there usually isn't a reason to walk on it, other than taking a shortcut of about 10 steps if you are going around the corner (he lives on a corner lot), and of course, ANY time you walk on it at all, it obviously does SOME miniscule damage, as opposed to not walking on it at all. But he really doesn't care.
Person C takes meticulous care of his lawn to have it be a play area for the neighborhood kids. Given the time and expense he puts into it for that purpose, he is kind of bothered when the kids DON'T come use it.
Obviously, stepping all over person A's lawn is a jerk move. He doesn't like it. Everyone knows that. So stepping all over his lawn is rude and inconsiderate. At the other extreme, stepping on person C's lawn is not only fine, it is expected. Definitively NOT rude to step on his lawn. What about person B? Really, no difference to person C in terms of being decidedly NOT rude (provided that one exercises reasonable care). CAN you just go around and take 10 more steps? Sure. Is it rude or lazy not to? Nope. Because person B (the person in charge of said lawn) doesn't care.
That being said, is it rude and pretentious for Person A to impose their morals on people who step on Person B's lawn, when it doesn't impact Person A in the slightest? Yeah, it pretty much is because it doesn't impact him at all, and the only person it does impact doesn't care, so it isn't a negative impact.
This is an excellent analogy, but I'll simplify it even further. In front of my house is a lawn. If you are in the street facing my house, the driveway is to the left, and the lawn is to the right. If you are walking to my house from right side and want to walk to the front door, you can either cut across the lawn or you can walk an extra 50-60 feet around the lawn and up the driveway (about the same number of feet I might have to walk to take my cart to a corral). I'm no lawn care expert, but I assume that walking on the grass does some negligible amount of damage to the grass (analogous to the negligible chance that a cart I leave will damage a car). However, I don't think I've ever not cut across the lawn. Does that make me lazy? Of course not.
Cmon guys, this is just shopping carts. You are going on about it as if it was a matter of life and death. Why not found a new religion for the people who put the carts back in the corral and for those who don't? 
That's kinda why I decided to chime in. I find it baffling that anyone gets worked up about this such that this thread is as long as it is!