I can vouch for there being a protected class bias. In my experience (Boston), using Uber while on crutches will cause your rating to fall. Even if you take full-service Uber’s (not Pool), and generally have someone to help you in and out and managing your crutches, drivers simply tend to rate you lower. Possibly because they have to wait longer, or because I need to lean on the car getting in and out, or because they need to keep the crutches in their car somehow.