I don't know if this is legally allowed in the United States, but your comment certainly applies in Japan. Over there, large companies should start doing that, but those companies are too conservative even with a law backing it. Only the small, younger start ups and crypto related business enthusiasts have done it.
For most of the world, first they need to address the legality barrier, because the first thing the employer will say, is that its illegal to do so. If the State doesn't even acknowledge bitcoin formally, someone getting paid in that could claim they are not getting any payment at all and sue over slavery and whatnot.
So after you get the law and regulation in place, it comes the really hard part to convince the employers to do so. It means an extra complexity to their management, which they would hardly see any justification spending money to accommodate for that.