In Nebraska we could direct-bury fiber up to eight feet underground with what was essentially a vibrating knife (pulled through the earth by two large Caterpillers) along the gravel paved county roads that were established when the railroads sold off land to finance their grade/track construction. It's incredibly cheap compared to any other means of installation and the right-of-ways are consistently available - https://duckduckgo.com/?q=vibration+cable+plough&t=ffab&iar=....
A tiny fraction of our fiber was mounted above ground (eight miles out of over 700 IIRC) but it was taken down by tornados/wind shear twice in the first three years after it was lit.