The reason is simple. It's extremely morally taxing to read the AI code and realize this is a mess that has to be scrapped.
Much, much more comfortable solution is to join the church of "I don't read code anymore":
1. You can ship fast
2. You can feel good about yourself
3. You avoid facing the uncomfortable truth
4. You get support from fellow believers
Slowing down to review the code feels like drudgery in comparison.
I'm in the review every line camp. I don't trust things that are addictive without a virtuous loop (like exercise). I have to interact with addictive things like video games, loot boxes, gambling, and alcohol in moderation. LLM use fits that perfectly. I'd rather use it throughout the day but still pause and feel the discomfort of reviewing the code, often throwing it out and having it try again when it inevitably makes a hot mess.