I know some people running independent community fiber ISPs. Digging trenches can be a nightmare depending on the neighbourhood. You can have property ownership issues, other utilities being present, permit nightmares, different ground/soil types, etc. That ignores the fact that when somebody else digs they can hit your lines and repairing that is a pain.
Digging is better, though. But it’s not necessarily as easy as one may think.
Where I work just acquired new property and are deploying a new site. It took 9 months, from date of first contact, before the ISP could come out, bore under the road, and run fiber to our building from two poles away. And that's just a short ~500 feet underground run.
I couldn't imagine the amount of permitting and logistics involved in trying to bury an entire run across town.
Overall, it's much nicer. No ugly telephone poles, don't have to worry about weather, just reliable, strong service. But to think it pays for itself in 2 years is laughable.