Bitcoin word on it's own is a very catchy and easy to remember word and people who don't even know anything about crypto are aware of this word like me in 2014.
Take Ethereum for example, it's a lil bit hard to remember for the first timers.
Lastly, we can't forget, it's the first ever cryptocurrency so it deserves the attention imo.
People are comparing new coins to a coin which was released in 2009, that's pretty obvious the newer ones would be better than Bitcoin, so you can ask why only bitcoin still, but again it was the first ever cryptocurrency and every new comer buys It atleast for once, which is not same case for other coins. It will take a long time for any coin to beat it.