This seems to be a question that comes up a lot. But it misses out on some details.
I think when comparing ADSL/FTTC to FTTP most people are looking at it from a purely speed factor. The other major factor is the different technology on how this is delivered. Also the amount of faults will drop when we're all on a proper full fibre network.
As far as people not paying for the higher service. I think that could be put down to two things. 1. Can a line actually reach infinity 2 speeds, and if so by how much? The second thing is real world line quality.
There are probably many lines that are listed on the dsl checker that says they can reach Infinity 2 speeds but in reality they might get 60MB. So technically you could order Infinity 2, but in reality you're only paying for 8MB above Infinity 1. So on the stats sheet it looks like you chose to not pick the higher speed.
I think the mentality of people only wanting to pay for cheap broadband is a chicken and egg situation. When marketing is always pushing cheap prices on packages that can do everything you want then the whole question becomes more about price than having a better product. I think as time goes along more and more people are becoming educated about ISP's and broadband just like they have done about the Internet.
The paying cheap point is interesting in that people are buying other technology that they don't need and is way overpriced. But they still buy it. So if this only paying for cheap broadband phenomenon is going on then it is uniquely only happening in broadband and we should ask why.
I think this issue is interesting and well worth it to keep monitoring situations. But there is a real danger of using PAST statistics to drive future technologies. People don't like moving to new things. That's a general point on anything. Very few people embrace new things. We could use the same arguments about adsl2+ which can go 'upto 24MB'. So if the people pushing this argument won we wouldn't have had FTTC, as currently 24MB would be suitable for peoples needs.
We know what is coming down the line in other technologies. 4K TV's are a thing these days. There is a gradual moving to IPTV channels, especially with Sky embracing Internet channels along side their satalite dish. We also know everyone and their grandmother is going to be online soon. We're approaching the point now that the oldest generation of a family will be tech savvy. We know the gaming world are wanting to delivery games you can play through a 'dumb' terminal, so you dont have games loaded on your pc/console, but play them remotely over the net.
If network providers don't embrace full fibre technology then they are going to be left behind. Whatever peoples habits are a network builder as to keep ahead of the game. If the people in charge don't like embracing change then they need to work somewhere else imho.
Demon => Freeserve => Pipex => Be => Sky => BT Infinity 2