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.
This is quite normal, indicating that the block chain technology is really promising, which leads to the mixed results of the projects involved. Most of them are just following, and want to earn a wave and go away.