I find an explicitly identified "BLUF" section to be annoying. I can read. If you want to put the most important information or request up front, just do that.
To be clear, I’m not putting a section literally labeled “BLUF” at the top of every email. This is more about a mindset going into the writing process, and ensuring that I always take time to include the most important information in the first paragraph.
I do use section headings later in long emails to help visually break up the content and help the reader skim/find what they’re looking for.
It would be annoying to begin every email with something labeled BLUF. Although I personally wouldn’t care if it would help more people actually put the bottom line up front.