Do we need altcoins?

If you look into altcoins like SOL, DOT, ADA, ATOM, etc. all of them sound good. In fact all of them sound promising enough for many people to think they will thrive in the future.

But will they? Do we really need any chains besides ETH? I could Imagine BTC will always be dominant where ETH serves for further usecases.

ETH is upgradeable so it can change with the market, while BTC has the potential to be solid and strong. So I read some stuff about these coins but I can't see a reason why we would really need them? They have their upsides like scalability and interoperability. But while ETH is evolving what do they offer to replace ETH and/or BTC one day?

I could see them surviving in their niche and it would be good for the competition. A downside is that too many different tokens complicate the market for investors and users. But why should I invest in them? I really don't see them rising to take over the market.

What's your opinion and knowledge about this? I'd really like to learn from your perspective.