Sadly my hostel is not wheelchair accessible, although we are considering installing a ramp at the front of the building so that at least part of the property would be.
I recently visited Tattva Design Hostel in Porto, Portugal. They had elevator access to upper floors, a roll-in shower in one of the private rooms, and a chair lift up to their rooftop terrace. I'm not sure if any of the dorms were also accessible or not.
We have only ever had one guest in a wheelchair as far as I can remember. Do other hostels see a lot more of this?