LLMs in industry

I dont have much experience about LLMs. But i see the requirements for LLMs in many job postings now. I was curious as to what the extent of LLMs is in the industry and what is expected? do majority of companies (maybe minus the faang or equivalent companies) just do finetuning existing models like BERT/GPT or do they actually build LLM models?

bert companies datascience experience faang finetuning gpt industry job llms requirements