The frontend feedback is much harder for AI. AI needs to be able to see the page with all the moving parts and sounds and have a bit of sense for the layout and taste in colors etc. I think it much harder for AI to recognize what feels good for the human user. Backend is devoid of that personal touch. By definition you are building for the machine. You have APIs, databases and infrastructure which is logical and easy for LLM to interact with. "All it needs" is curl and it can run in a loop the whole day improving backend software.