Companies that aren't mindful of vendor lock in aren't long for the world.
Though those cloud platforms all have their own proprietary components most users are savvy enough to constrain and compartmentalize their use of them lest they find themselves having all their profits taken by a platform that knows it can set its prices arbitrarily. The cloud vs in-house adoption is what it is in large part because the cloud offerings are a commodity and a big part of them being a commodity is that much of the underlying software is free software.
On the other-hand, companies that fall behind their competitors because they are spending time on adjacent activities rather than leveraging new capabilities on the market will also lose out. It isn't clear at this time that LLMs fall into that categories ... and smart applications of in-house systems can be as much as an advantage as badly done NIH projects can be an albatross.
History is littered with companies that went dead because they focused on things that don't matter (open source, anti-microsoft, pro-linux).
There will be a time when those things matter when it hurts the bottom-line (Dropbox), but to prematurely optimize for that while you are finding product-market-fit is crazy and all companies are finding product-market-fit in the new AI era
Though those cloud platforms all have their own proprietary components most users are savvy enough to constrain and compartmentalize their use of them lest they find themselves having all their profits taken by a platform that knows it can set its prices arbitrarily. The cloud vs in-house adoption is what it is in large part because the cloud offerings are a commodity and a big part of them being a commodity is that much of the underlying software is free software.