> I'm still wondering why Lambda simply doesn't support Docker containers? Would put an end to all this requests like "Please support $my_favorite_language on Lambda"

Because they can present that as a separate service (Fargate) and bill more for it.

Fargate isn't exactly what you're describing, but it's a close match. It's in Amazon's best interests to charge people based on the amount of "DIY" they're willing to put up with, and that's why they offer a number of overlapping services at different price points.