There are 88 of these inside a piano, one for each key. Pressing down on a key (58)... does nothing. You literally must strike or hit the keys to get any sound. This is because the release mechanism is set up so that hitting a key results in the hammer (6) flying up and hitting the string (1) but then falling away so that the string can resonate freely, as long as you hold down the key. Once you release it, the damper (2 & 3) comes down and presses against the string, silencing it. Pressing a key slowly either causes slippage resulting in no action at all, or just causes the hammer to rise up and press against the string, and since the hammer head is made of felt, it will stifle the string.
My point is that there is a technique which must be mastered before you can get beyond just plunking out a melody. Pianists' fingers do these things automatically, because if you actually had to think about it, you'd never be able to play anything. It's all muscle memory.
If you know the notes and the keys, that's a good start, but that's all it is. Actually working the instrument, controlling what it does via the keys and pedals, is what takes years of practice. "I know how to read music and hit the right keys" is not the same as "I can play the piano". An electronic keyboard can help you learn the notes, but practicing pushing plastic keys down will do little towards teaching your fingers how to work actual piano keys, other than where the keys themselves are. It just seems to me that it would be really hard for one's fingers to make the transition.
When I was 10, I took piano lessons. I learned to read music and played a 3rd-year piece at the class recital, which was three months after I'd started. Being even more arrogant and obnoxious than I am now (imagine!) I decided that I had learned to play the piano, which is what the lessons were for, so I quit. The idea of taking lessons for years and years just seemed stupid to me. My sister went the other way. She took lessons for years and years, studied with Van Cliburn, and at one time considered a career as a concert pianist. She can play anything that's written, but cannot play a single note without it being written down in front of her.
When I quit, what I didn't realize is that those stupid pedal exercises that my teacher made me do actually taught me proper pedal technique. Those scales, literally running up and down the keyboard over and over, taught my fingers fluidity, and also consistency. The harder you strike a key, the louder the note is played, and the goal is to make everything smooth. My teacher assigned lessons from each of four books every week; pedals studies, scales, and two different method books. I didn't realize it at the time, but she was a great teacher.
I've seen and worked with kids who took piano lessons, sometimes for years, but they can't play a piano. They can play notes, but they can't work the pedals, and there's no dynamic control in their fingers. You can't learn that on a plastic keyboard.
Okay, I'll shut up now.