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
I don't think so, altcoins can change the value of bitcoin(for more or for less).
For example, an altcoin can bring attention of the public that don't know bitcoin yet, and after some time they can learn more about bitcoin and start to use it and the price goes up, or, people can buy alts with bitcoin and the value goes down...
But imagine investing all those millions of dollars that solicited by altcoin projects in bitcoin instead. We would be far from where we are right now.
Scam coin has been a trend ever since and I think that just decreases the price of bitcoin. The bitcoins that the devs have collected will be converted into fiat no matter what the price is. I think bitcoin would be much better without these scam coins covered by the name "altcoin".