Is because the name "Bitcoin" is the best name for a crypto-currency.
No other name will be as good.
Not agree with you, what will happen if Bitcoin die tomorrow will all crypto currencies die? No right if Bitcoin does not exist in future than there will be another crypto coin. Well Zcash is also good name isn't it?
Out of all the Alt-coins, I like Monero the best. It sounds nice in a variety of languages. Even still, it doesn't really describe what it is very well, although Monero is a very cool way of saying "money".
Bitcoin sounds good, and perfectly describes what it is. Whoever came up with it is brilliant.