We all know that Bitcoin price do affect the general crypto market which makes it a superior above every other coins or tokens in the market. When the Bitcoin price falls, all other tokens and coins will fall too due to strong affiliation of Bitcoin to the crypto market.
Most altcoins came in the market after BTC funded them through their investors. So its a sentimental value which exists.
After that the altcoins were expected to do something that will allow users to do something different and new, but of course that never happened so they remains pump and dump schemes and being funded by bitcoin, they follow bitcoin's price changes.
If any altcoin could have solved a real life problem then that coin would have become a different entity and bitcoin would seen a competition but that is rarely the case now. Any project that attempts to copy what bitcoin has been ends up the same way.
So folks, buy bitcoin and hold for long.