AI emails demonstrate your lack of effort.
Typically, people email me because they want me to commit my valuable time to doing something that they value. Sometimes, it’ll be a win-win situation where someone sells me a solution to a problem that I want to fix. But before I know if this is worth my time you are effectively asking me for a favor. But if you yourself care so little about it that you cannot be bothered to write a short email yourself then you’re being unreasonable when you ask me to care.
Buying flowers is such a highly valued gesture because the flowers are unmistakable proof that you (or someone who is willing to help you) spent time and money. The fact that it’s cumbersome is precisely what makes flowers a sincere gift.
Or in the case of AI-generated email, the lack of effort is what makes it an insincere gesture.