SponsorBlock skips those. The downside is the video sometimes needs to be a couple of hours old before someone gets around to adding the skip sections.
Google doesn't embed or control those adverts and doesn't benefit directly from them, and they might not want to anger the minority of their user base with this addon any more than they already are by forcing yet more unskippable ads on them.
If the seek bar was disabled while a "this video is sponsored by" segment started playing, I would just stop using YouTube immediately.