As an ISP: right of way and economics of $ per last mile customer reached are HARD. The incumbents in an area, generally the copper phone line company (ILEC) and cable TV operator (Comcast, RCN, Charter, whatever) were handed the aerial ROW and underground ROW on a silver platter 30+ years ago, when there was no such thing as telecom competition. It was just assumed at that time that those two companies would be installing stuff on the same poles as the power company.
They built wherever they pleased, whenever they pleased, at minimal regulatory cost and with minimal additional costs. Because of course nobody would buy a house with no dialtone phone and/or no cable TV.
Now in a modern era if a FTTH ISP wants to come along and overbuild the same routes as the phone company, it's a lot more difficult, time consuming and expensive.