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?
Bitcoin is the most popular of all the digital currencies because it is the first of them all. Without bitcoin, I don't think that there will be an emerging digital currency. Also, as the first and original digital currency, it has the highest price of them all, so the tedency of the users are to be attracted to it because it has the most price.
it was already proven and it implements in a lot of country now, it does offers good opportunity to every nation.
Bitcoin is the most popular cryptocurrency because it is the best crypto. BTC is voluntary, decentralized, and open source. It also has the best community behind it. Wallets, developers, etc all want to make the network better. That is not the case with others, except Monero, but even then it's greedy. Why not just help build anonymous txns on BTC? They're here now, but coming for everyone soon so I don't get it.