You sort of miss the point that their "need" is to get in to a house. That is the same as everyone else. The means by which that is achieved is a matter of practicality. They don't need a ramp, they need to get into the building. The ramp just happens to be a practical and economic means of achieving that. Much like stairs are for able-bodied. The need is the basic requirement, not the means by which it is achieved.