Finetuning, as I understand it, is mostly laborious and mostly very boring and exhausting work that is not appealing to many engineers. It can be done by people who have some skills in Python or similar language and who have some background in statistics.

OTOH to build the infra for LLMs there's much more stuff involved and it's really hard to find engineers who have the capacity to be both the researchers and developers at the same time. By "researchers" I mean that they have to have a capacity to be able to read through the numerous academic and industry papers, comprehend the tiniest details, and materialize it into the product through the code. I think that's much harder and scarcer skill to find.

That said, I am not undermining the fine-tuning skill, it's a humongous effort, but I think it's not necessarily the skillset problem.