Directly from many venues. And some ticket sellers that aren't owned by them. Some smaller venues use them, and some artsier places.
But for the mega concerts, I just don't go where Ticketmaster holds the venue contract. I fly and see who I want elsewhere.
If it affects system performance and gives me no noticeable benefit. Otherwise, flash bytes are cheap. I've got 30TB+ in my laptop. Why do I care if I have a 3GB OS or a 2.95GB OS?