People create their own coin out of necessity, the blockchain technology is useful and cut across other businesses/sector of the economy. Although this seems to be a recent trends, the more ideas that involves blockchain, the more ICO's thus more coins in the market.
And you know ideas can't just cease, but some ideas/project are just copycat.
More ICO are on the market and more Ico are starting to take shape and people are competing to make their own coin means that crypto is now more and more interested and has more potential. so it encourages them to participate in cryptocurrency