It is:
1. You have to build your fibre backbone anyways. That's an even bigger trouble in countries with no culture to share fibre. And you would usually have to get much "brainier," and more expensive fibre equipment in this case.
2. You still need to wire the fibre fairly close to premises.
3. High speed copper network equipment costs huge sums, more than commoditised GPON.
4. Copper often needs to be torn, to be replaced with higher grade copper
5. You still need to drill buildings to install niches for copper equipment.
6. You need to put extra equipment into equipment closets.
7. Copper needs more equipment overall
8. Copper has lower reliability overall, and costs more to maintain
So, in the end, you just do the same FTTH, just with copper as the last few tenths of metres. This is so obvious, but people keep dogmatising over "it's already wired with copper."
GPON by comparison does not require anything in the closet, but a piece of glass passive optical slitter.
You can easily have 1024 end-users on a single powerful GePON OLT, covering few square kilometres of 100% passive net.