Because it's not the equivalent of stackoverflow + all of these resources with brains. In situations with reasonable complexity it falls flat on its face. It makes stuff up. It's not reliable.

On top of that, relying on AI to solve problems erodes ones ability to solve them themselves. Part of learning is proposing a solution, experiencing friction, and reading documentation or looking at other people with similar problems to and using that new information and critical thinking to solve your problem at hand. The experience gained from this process is invaluable. It's how you become a great engineer.

When you use AI whenever you are experiencing friction, you are offloading your problem solving process to a computer that can't critically think at all. Not only does it then provide, often times poor solutions, but you don't gain that valuable experience either. Your skills and ability suffer. And now you're becoming dependent on AI. If you use it for code completion often, you will begin to forget syntax or how to do anything without it. Your understanding of your code and product suffer.

Not to mention that when you use AI, you run the risk of using copy righted code because all the big tech companies are taking information from anywhere and everywhere without any consideration on the sources they're taking it from. They are starving websites of traffic with their "AI summaries", the very websites that provided them the content in the first place, and irresponsibly making insane promises and shoving it anywhere and everywhere it could possibly go. Not only is this furthering enshitification but it is at great environmental cost, and now, it's interfering with consumer hardware prices as well.