Re: What are people doing that needs fibre?
A family of four will swamp a 40Mbps line just with base level streaming, background browsing software updates, etc.
In my household with two teenagers who are into multi-player Xbox games, Amazon Prime and YouTube, plus parents who think nothing of video calling/conferencing and running concurrent RDS sessions; we've yet to top out our 38Mbps FTTC line. However, I am aware that there are times when contention beyond my FTTC circuit causes things to slow down - and does it really matter that a Win10 image download or the recent Xbox update takes circa half an hour rather than a couple of minutes?
So whilst I don't doubt there are households who can swamp a 40Mbps line, I suspect they are (currently) very a small minority.