Because when you do, men say no more often than not. It rubs against their ingrained notion of being a "hunter". They really don't do well on the other side of the fence, but the grass is always greener right?

And yes, I've asked dozens of men out. Only one said yes right away.

Ironically, after they turned me down, many them asked me out days or weeks later.

Just goes to show that building trust is not an exclusively female need. Rolling up on somebody and making romantic overtures is inherently distressful to the receiving party. Especially if they weren't thinking about it beforehand. It's never not going to have a weird vibe to it.

Better to get to know someone first or not treat a request to hookup like a date in the first place.