If you currently use a wheelchair or know someone that does, then you know how hard it can be to take a shower. It is very difficult to get in a tub without assistance, and the whole bathing experience is just very hard. However, a "Roll In" shower makes this much easier.
One reason for this is because there is no ledge to step over, so you or the person you know can easily get into the shower. "Roll In" showers also tend to be quite large, and it is easy to find a model that is large enough to accommodate a wheelchair without feeling cramped.