Why oh why do we do group projects in grad school?

You know, in high school, I loved group projects. Probably because it was pretty easy...assinging people work, getting to hang out in the process, and having fun. During my undergrad, when group projects were assigned...I started to think...this is really difficult to organize because everyone has a different schedule and I'm busy with my life and my activities, and whatever, I'll deal....and it always turned out great, and I think even during it, it was fun to be going through the process with someone who knew your struggles exactly! Now, here I am in grad school and am being assigned group projects left and right and I'm thinking, "LAME! Who does this!?" I mean, let's be serious people, now the stakes are higher, people have even more difficult schedules to accomodate, and people don't even live in the same area to meet up when you DO get time. I enjoy group presentations, but they are just so difficult to put together. Not to mention...and this may come as a suprise...there are still people, even in grad school, who slack off. Now, if this is you who is reading it...well...don't do it anymore! Those people who can't follow directions or turn things in on time...they still exist. And you know, it's partly my own fault, because I get sucked into the role of leader because it's in my nature, and then have to do more work organizing stuff, and having to tell people "3 PM Sunday was 24 hours ago, and you STILL haven't submitted your section!" I don't get it. I don't get how professors can still assign group projects with the design of this program, or how I can be sooooo NOT understanding. I guess with my clients, it's different because I'm more separated from them, but now, in this group situation...I am feeling overwhelmed and disappointed with the students I work with. Maybe this is the problem with having high expectations...or just being a control freak. Ha. Okay, rant done.
PS SOCIAL WORK STILL ROCKS! hahaha, despite all that, it's still good people. Seriously. hahaha