And how ignorant to say you shouldn't invest in crypto if you don't want to spend them.

The problem here is the mindset. You're thinking that fiat is the only accepted currency (which it is) and that crypto is just an investment. It's especially valid here since this converts crypto to fiat.

However, think that bitcoin was made to be a currency, not a store of value. Sure it's becoming that right now, but that may not be the case for all cryptos. Some of them are designed specifically to be used as electronic cash is today. From that point of view, "why buy them if you can't spend them" is a little more logical. If you kick it up a notch and get your salary in crypto (I used to get 50% of my salary directly in crypto 4 months ago) then why not spend it when it's literally your currency?

There's also another reason why one would like to spend directly from one's investment in a bull market with little fees, akomba explains it here

I don't disagree with you in any way, I'm just saying that changing the premises a bit change the conclusion. You're right from a classical point of view, but things might change =)