BlameThePixel!

Well then we have at last a riddle that requires questions. Yeah!

That's right but why?

Because he was tired of being short and having to walk these three floors?...

Not bad answer but incorrect.

Hmmm, well for some reason he was able to go to the 7th floor this time.

Did he have a girlfriend who was slightly taller than him, and she pressed the 7th button, then at some point she told him she was breaking up with him, so he committed suicide?

Or did he wear special shoes, perhaps with springs on the bottom so he could jump out his window. The shoes could also explain how he could reach the 7th button. It doesn't answer the question of why he wanted to commit suicide though.

He didn't have a grilfriend, he didn't wear special shoes.
Find out the reason he could reach the 7th button and it'll help you realize his reason of the determination to commit a suicide.

The man was a professional jockey, he loved it, and it was basiclly his livelihood. When he grew tall enough to press the seventh button, he realised he was too tall to continue being a successful jockey, and devestated, he decided to commit suicide by jumping out the window.

Very close...

Did he grow too tall for his favourite kid's ride at Disneyland or the mall or somewhere?

Was he a professional in some midget sport like midget bowling, but then he grew too tall to be classified as a midget any more? Or perhaps some other midget group like a midget dancing troupe or smething?

Or was he a movie star, but then he outgrew his role as a midget or hobbit or whatever?

He grew tall enough to reach the 7th button, but because of a back injury he sustained earlier he couldnt bend down. His sudden growth spurt meant that he couldnt reach the first floor button, and there are no stairs down to the first floor. He was thus incapable of getting out of this flat unless...

Solved

The higher numbers must all be in one column going up, otherwise when he grew taller and was able to reach 7, he would be able to reach 8 as well.

Maybe he likes the fact that he can't reach the higher buttons, because that gives him an excuse to get a little bit of exercise going up the stairs. He might be too embarrassed to be seen using a stick.