I believe that they're popular mainly because well it was the first of all cryptocurrencies to be made. Honestly most of the other coins are scams and greedy ways that the developers make money. The only other coin I can think of that isn't a scam are dogecoins! What do you think?
Since this is a bitcointalk forum, and Bitcoin is the pioneer cryptocurrency which has a very high value and made a lot of people rich, that iis the very reason why it's popular
