Leetcode implies complex, contrived algorithm scenarios presented to be taken apart in a brief interview (usually at most 40 minutes for the coding question). Real world scenarios do not resemble leetcode questions, and hard real world problems are solved with more time and careful thought.

This creates serious inertia. Once you are 3-4+ years into a job, you probably haven't done much leetcode studying in a while outside of you doing interviews yourself. Interviewing at other companies is actually a pain in the ass, so it's often not worth the bother.

It's automated and mostly mindless. They are looking for "smart" solutions, that fail to account for testability and code maintanance.

I fail a lot of leetcode challenges, yet I've built a critical data platform for Grubhub, IBM, Expedia, etc... some are still in operation to this day.