> you can use their LLM to trivially clone their software.
Perhaps, but what you can't clone is familiarity, polish, integration, and network effects. These companies desperately need a moat, and so for example all the new additions to Claude's web interface are becoming the products that the vast majority of people will use and be locked into (if it goes according to their plan).
If development is trivial and capability remains the differentiator, then "familiarity, polish, [and] integration" are non-issues.
I'm not sure what network effects even means in the context of llm selection.