Allowing a user to bring their own key to a backing LLM over-complicates the product for the developer. Now, instead of managing your account with them, they al

Allowing a user to bring their own key to a backing LLM over-complicates the product for the developer. Now, instead of managing your account with them, they also have to manage your account with the LLM provider, and they will be restricted by the limits of that account. They can't take advantage of any economy of scale by using their own keys and accounts. It's a huge mess and security nightmare to hold keys for other users and usually not worth it, unless that itself is your business.