Bitcoin doesn't need altcoins because it was making its way by its own.Altcoins are dependent on Bitcoin which has been seen over and over again on every rise in price of Bitcoin.Bitcoin will always rule the digital/crytpocurrencies no matter how advanced they will be in tech but still will remain under Bitcoin
Be sure that without altcoins the bitcoin couldnt be such sucess, people joining crypto world and investing huge ammounts of bitcoins into others currencies, expecting to get more bitcoins in the process, or get rich, something that only bitcoin allowed in the past, nowadays we can get and make a good result investing into altcoin.