#1 I feel it’s impolite.
YMMV. They’re putting in their valuable time to help me—don’t they deserve a clean copy to help along their reading experience?
#2 My rough drafts are way too rough.
I’d feel bad, frankly, to make people go through the copy I have to go through, every time I work on editing a fresh novel. It’s not just that my sentences are long (even though they are), nor that I keep slipping short words from the middle of sentences (which I do), nor that I tend to lose thread of what I wanted to write in the first place and then. I write something completely different. It’s pain.
#3 I’m too afraid that my friends will give up on me…
…at a certain point, if I send them too many rough drafts. I write. And I actually write often (when I’m not hibernating). And I seriously value my first readers, because they’ve been known to catch issues I wouldn’t have even dreamed of. (Thanks!) Not everyone I manage to enlist as a beta even reads in my genre(s) of their own volition, and I really appreciate them doing so for me!
#4 I prefer control.
And doing my own line edits before sending the drafts out makes me feel like I’m actually keeping at least a part of the control. Yes—it means doing both blunt edits (plot, characters and infodump cleanup) and line edits before I send anything out. In a way, it’s making me write cleaner copy from the get go.
#+1 It’s forcing me to write cleaner first drafts!
If I’m the one who has to swim through the wasteland which is my first draft, if I’m the one who need to keep an eye for every stuping, machine unreadable mistype (wary and vary and very and weary are the best examples I can think of), if I’m the one who has to figure out what’s going on in a scene I don’t even remember writing… come on. Who wouldn’t learn to write more precise first drafts anyway?