Thanks to Sky's work-at-height policy, most dishes aren't more than 8ft off the ground these days, so it's not a major hassle to swap out an LNB for one with more terminals. Having said that, mine's right up on the chimney breast. Sitting up there on a roof ladder isn't very much fun.
The reason people go for Freeview over Freesat is that the Freeview brand is more pervasive and persuasive - it has been around for longer and uses familiar technology. Satellite dishes are still 'newfangled' to many and 'common' or 'tacky' to others.
Nevertheless, you're right, Freeview is already out of bandwidth and much shoe-horning has already gone on to try to wring more out of what they have. Meanwhile out in orbit at 28.2E, Astra 1N is about to go commercial, offering tonnes of narrow spot beam capacity to the UK.