Why disable people consider themselves normal?
This is a horrible question. "They" are very much "normal".
Just because an individual has a visible disability doesn't mean they are not "normal". There are many individuals with unnoticed/inner issues or disabilities and this does not make them any less "normal" you just cannot see there issues to be so judgemental towards them. Who says or gets to decide what the definition of "normal" is anyway.
Very, very shallow and ignorant of you to unfortunately feel this way.