I watched an interview with Mayim Bialik where she said, "Hey, with a nose like this? I knew I wasn't getting anything after Blossom but character acting parts. It doesn't bother me. It's work."
From having been in theatre/acting classes before, when people were cast for a role they took it as a "job" of sorts. It wasn't anything personal, and hell, some people (like Seth Rogan) have cashed in on their hilariously bad looks (although I'm not implying Mayim looks hilariously bad -- she's one of my personal idols because girl's got style on and off the set).
Theatre people are generally really good about this too. It's all about the craft; in a group of actors/actresses you're more likely to hear, "I could really feel the lines from her" than "She looked perfect for that role..glad they cast her as the Hot Girl." If I had to guess, I'd say that said fat/ugly/etc actors/actresses don't get too hung up about it.
Maybe it's different on a bigger scale (I'm thinking like...promo deals stuff like that..maybe you'd feel badly if you weren't getting roles anymore AND your line wasn't picked up or you weren't chosen as a spokesperson to further supplement your income for example), but I think actors/actresses are mostly just happy for work. Plus, if they consider acting a craft, they won't give much thought to the typecasting of the role itself -- they'll give more thought to doing the character justice.
source :- quora.com
