Why do few remember the rocker Michael Coletti?

Because technically, there was no rocker Michael Coletti. The man born with that name had it changed to Steven Adler when he was a child. The last name came from his mother's new husband. The first was changed to follow Jewish tradition, so that he was no longer named after his father.

Why do few remember the rocker Steven Adler?

Because after being one of the first members of Guns N' Roses, he was fired from the band in 1990 due to a heroin addiction.

And if you are so drugged up that you get fired from Guns N' Roses...

Maybe it's good that few remember Steven Adler.

Or Michael Coletti.