I agree with you - we are saying the same thing, by restricting their API or making less developer friendly, they want you to be captive in their UI. This might not be true for Anthropic or OpenAI - another child commenter made a comment about ads in CLI, I would not be surprised if in a while we will have product placements in LLM responses exactly as we have it in movies - not a plain ad but just a slightly less subliminal suggestion.

It’s objectively easier to build a frontend now and therefore that moat is disappearing. What you can argue is the moat is in incumbent advantage at the UI layer, not the UI itself.