Supply and demand, and as @grumpyfish, “marketing” has something to do with it, too.
On a plane, especially the long route ones that normally fly closer to “full” than not, there are a limited number of ‘business class’ seats, and they are deliberately limited and disproportionately served with cabin attendants compared to seats in coach. So they command a higher price because of scarcity and actual / perceived luxury.
There are a lot more “business” hotels (as opposed to “resort” hotels) than airplanes, and for that reason most of them typically have a much higher vacancy rate. So the rooms themselves can’t command the premium prices that planes can, because many hotels may serve a given city or locale, but relatively fewer planes. (Notwithstanding that not all travelers travel via plane.)
Then as @grumpyfish stated, “business” means something different in a hotel: business travelers don’t spend all day in the room, as a rule, and don’t demand excessive service. They spend the night sleeping in the hotel, maybe using the restaurant and bar (big money makers for the hotel—generally money-losers for the airlines) or room service, then leaving during the day for their business.