Because seeds are ridiculous expensive, clones even more so, and I grow outdoors. I'd much rather spend $100 once for 10 seeds, get a few males, pollinate a few buds on the girls, and end up with hundreds of seeds.
I do buy a fair amount of clones. But as an outdoor grower they're a pain to time. I was at the dispensary with a buddy, who was buying some plants, the middle of June, so just for ducks I picked up a Plantinum OG and put it outside. Within 3 weeks it had flipped to flower, stopped growing and is at 3' now. Be lucky to get an ounce out of it. (I'm sure it was getting 24hrs of light when I picked it up.) On the other the hand, I have a bunch of NY Afghani seeds I made a few years back. I actually don't really like the buzz (big snooze fest IMO), but I was fooling around doing some germination test the middle of May. I threw out all the little plants after a couple weeks - except one. It's in a 10 gallon pot, never got much loving, and is over 6'.
It's not so much that the clones suck or aren't as good, but rather the timing to move them outside is always problematic for me. I started a mother (from a store clone) in March, made about 10 clones from it in May. By the end of May it outgrew my little indoor grow area, but I couldn't move it outside that early. So then I had to spend a month hauling it outside in the day, giving it extra light in the garage at night, until I could safely plant it in the dirt. The whole rigmarole of weening it from 18 hours down to 14 was a pain - making sure I was home to move it back inside at dusk, etc.
Seeds have their own issues - like having a 6' male. I've actually had to clone up males because they got so big and I just wanted a little 2' for pollen, not a tree. But it's great when you get a huge seed haul from a strain you like and know you'll have it for years (without having to keep a mother going).