I think 18-22yo who do startups are more likely to have something they're passionate about and build something awesome for the long haul.

The 22+ yo who have graduated college and need to find something to do, or those who have worked for one startup and now want to do something (but don't now what), seem a lot more likely to do a "fund me!" perfunctory startup.

I don't think it's really that related to age, though.