Takes time for one thing translates into tons of other reasons... OK.
1. Time
2. If you're new to photography, shooting in a semi-auto mode helps you learn before trying full manual (speaking from personal experience).
3. When you're not sure what to do... not everyone has been at this for years and years or grew up on manual only cameras.
4. Sports photography, where everything is fast paced and changing regularly.
5. It's simply not necessary all the time.
6. Variety - when you are uncertain what your subject is going to be. I do photo walks nearly every day, sometimes I photograph a flower and at a moments notice a goose or duck flies by, it's much easier and faster for me NOT to be in manual mode to get the shot off. Even the commonly recommended book 'Understanding Exposure' points this out multiple times.
All valid reasons, and I'm not saying you can't do them in manual mode so don't assume that.
I agree, those are all good reasons. I just think the other modes are stepping stones to full manual. Or should be.
Number 6 doesn't hold a whole lot of water with digital, you can get away with a lot and still get a great shot. It might have been true when talking about film, especially slide film, but not so much with digital. Also, I have shot sports and exposrue doesn't change that fast that you can't go manual, in fact I shoot sports with manual focus because of the problems with auto focus.