I feel like being at the bottom of the value chain is a mis-categorization. If you consider base LLM model as their sole offering I agree with you, but these companies have shown an eagerness to eat their way up the value chain. Agent mode, Search, Study Mode, AI code editors, are such examples of products that could be higher-on-the-chain startups but are offered in-house by OpenAI.

This reminds me of Amazon choosing to sell products that it knows are doing well in the marketplace, out-competing third party sellers. OpenAI is positioned to out-compete its competitors on virtually anything because they have the talent and more importantly, control over the model weights and ability to customize their LLMs. It's possible the "wrapper" startups of today are simply doing the market research for OpenAI and are in danger of being consumed by OpenAI.