but they all seem to be countered with “but that’s expensive”
And time consuming and more difficult to assess, maintain, modify, and install. While increasing the underground footprint which makes it more difficult for other underground utilities and construction.
Well there are many compelling reasons
And when the reasons are good enough the lines go underground. Otherwise yes the cheap and easy way is better as the baseline, because paying ~10x more and taking much longer to install a system that is harder to work with for no good reason is stupid.