Remember those are all theoretical speeds. The actually speed you get from a tower will depend on a number of factors.
Signal strength you are receiving.
The amount of users currently attached to that specific tower.
The amount of backhaul (bandwidth) that tower has been allocated.
The tower can support 42.2 mbps speeds, but if there is not enough backhaul and that tower is extremely busy, then you're not going to get those speeds.
And I don't think it's just limited to the rural areas. Even in the cities, people struggle with speeds even if the tower supports super fast speeds. If the tower is busy and there is only limited bandwidth available, it's going to give slow speeds no matter who you are.
I think for rural areas, the problem lies with getting backhaul out there, as there are no fibre links or piping to provide the bandwidth to the towers in those rural areas. Those towers usually rely on microwave links to connect all the towers to a signal tower that is connected to a fixed line backhaul.