What it came down to for me was waiting until I was no longer dependent on my parents for me to get a bike. They paid for college, and I had this crazy idea that my edjumahkashun was more important than riding a motorcycle (in the long run.) They said that if I did buy a motorcycle then the rest of college was on me. I love my parents AND respect their wishes, so I didn't push it. I survived those bikeless years, though riding on the back with my friends was only partially satisfying.
I bought a bike about two weeks after I got married and we have had no less than two motorcycles in our posession since then.
Kids are in the far future, but we've already decided that while we'll supply them with pocketbikes and dirtbikes, their first street legal bike will be their responsibility. We view motorcycles as recreation and a priveledge, and want our kids to not be given everything. So, if they're 18 or 19 and can afford the bike AND insurance, then we'll support them.