You're not wrong, but most of the big players will take a while to switch, at least in my experience you have to put more effort into making sure your prompts result in what you want, and that's annoying especially if GPT4 is already working for you. Claude historically has really bad refusals for safe prompts.
Also, GPT4 is cheaper 10/30 $/m vs 15/75 $/m for claude 3 opus - I'm not sure that price hike is worth the _slight_ benchmark improvement.
GPT-4 has little "lock-in" and isn't "good enough" the keep users via inertia.