Reason number one:For pump&dump purposes.
Reason number two:Exit scam ICO(which is kinda like the first one,but with pump&dump they could pump the coin again and gain aditional profits).
Those are the real reasons.The fake reasons include:instant and cheaper transactions,easy and profitable mining,technology innovation that will beat the crypto competition.
Exactly!
But being on the positive side, a lot of new cryptocurrencies have been developing as it tend to adapt convinience for their customers. That is, if the project is also a success which most of them are much alike and lacks uniqueness.