More to the point, helicopters and power lines have both been around a lot longer than helicopter autohover technology, and aviation is an inherently conservative enterprise. Even if these sorts of repairs are being done using autohover today (I don't know) they were surely flown manually in the past.
UPDATE: I asked this question on /r/flying and got this response from an actual helicopter pilot:
https://www.reddit.com/r/flying/comments/998c8b/helicopter_p...
"In a low energy state like an OGE hover, and especially when doing dangerous work like utility (as in the video), live hoists, etc we are almost always handflying. You would be surprised at how few helicopters out there are even capable of auto-hovering. We have an IAHAAS system on the Pave Hawk which in theory can do things like auto hover, auto land, maintain radalt and baro altitudes, even fly zero vis approaches etc. but we don't trust it. I have personally seen it do some sketchy things like virtually departing us from controlled flight during a steady hover for literally no reason."