I shoot both but predominantly FT because I'm not fond of lying down, and I am really not keen on shooting at a blurred target. This is due to having to wear glasses since the age of 7. I associate blurred vision with something wrong (I've not put my glasses on, my lens is smeared, my contact has slipped).
I do think incidentally and have mentioned in previous threads, that the no scope adjustment rule has unintentionally disadvantaged older shooters (or at least advantaged younger shooters) as the advantage of the focusing ability of young eyes is enormous.
However I do like the aspects of planning your shot: choosing the best shooting position and knowing your trajectory to the mm to thread the pellet through obstacles. If HFT had a separate class which allowed (but didn't force) a sitting position and scope adjustment I'd probably shoot it a lot more, as apart from kill zone sizes it would be closer to the early days of FT, but different from SFT. Back then I shot sitting but rangefinding by eye, parallaxing for a clear image and dialling in the range.
Another reason is I shoot springers and being forced into different holds is an extra handicap. The best chance of hitting some of the tiny kills is through hugging the peg, and the existence of the peg has pushed a move to smaller kill zones to make it harder for PCPs, but the POI shift of a springer tends to negate the assistance of a solid peg. That just highlights the prowess of the top springer HFT shooters like Paul Lawrence all the more.
A few words about the thing which keeps cropping up again and again; the mistaken perception of the cost of FT rigs vs HFT rigs. You don't have to spend £2k+ before you start the sport! The scope is the only real differentiator here; the rifle isn't an issue. An S400 with one or two home stock mods will cut the mustard, or spend 400 notes on a used AR20 which will be as accurate as anything out there. Once again you don't need the big scope to have a go at FT. You might need it to compete with the top boys but if you're new to the sport and trying it out you're not going to be challenging them anyway, and that's the same for HFT too. You can have a go at FT with your 3-9x40, even without shooting in SFT... just manage your expectations around dropping many of the longer targets. When you want to take the plunge with a dedicated FT scope, £200 ish on a Falcon T35 or £300 ish on a Bushnell 8-32 and you're good to go. Or even in many cases £100 on a Zos 10-40 will do the job.