Privacy is a necessary feature in my opinion, but why hasn't Monero become a main coin?
One of the things that I've noticed about Monero is that it has been removed from a lot of big exchanges.
My guess is that some people want to have certainty that they will be able to go to any mainstream exchange in the future and exchange their crypto for other type of money.
Having Monero out of the big exchanges will probably not incentivize some of the big players, therefore reducing the potential price.