I think the idea that LLMs are incentivized to write verbose code fails when one considers non-API usage.

Like you, I’ve accumulated tons of LLM usage via apps and web apps. I can actually see how the models are much more succinct there compared to the API interface.

My uneducated guess is that LLM models try to fit their responses into the “output tokens” limit, which is surely much lower in UIs than what can be set in pay-as-you-go interfaces.