I've purchased a few altcoins with differentiation and solid dev teams behind them. And it's still a gamble; I expect most to die off.
Same reason people buy deep out of the money call options or do leveraged FX trading - they just like to gamble. The whole FX brokerage business (and that includes crypto) is basically run like a casino.
Storj, which is in the same space, is a couple year ahead and is just starting to try and get traction (but had a management shake up)
The most serious alt coins are very much like startups.
Factom, which is sort of a digital notary service, seems to have been working for several years on their platform and only just recently picked a market- Mortgages- Claiming they want to prevent the problems that happened in 2009 by making auditing and verifying mortgage documents better. They closed their Series A last year, but did their ICO a couple years before that.