It's actually pretty common to need to buy things over $10k. It's pretty common for vendors to not take checks. It's pretty common to not have high enough credit limits to cover these types of purchases.
There still isn't any way to do this other than cash.
It's unusual to carry around this much cash every day, but it's totally normal to carry this much cash sometimes for specific large purchases.
That's a very USA-centric comment. Checks are virtually unheard of in Europe and no one would pay so much money in cash. You would do a wire transfer or a card payment for that.
Payments in cash to a professional from a French citizen have been capped at 1000€ in France for years with virtually no impact. I have never seen or heard of someone attempting to use that much cash.