Most people don't. There's a reason why most of the "full figured" porn stars are 30 somethings returning to the biz after retiring for a few years. For most chicks that look like that in the 18-24 age range, there are more lucrative career paths. Flipping burgers or a barista at Starbucks for example. For a chick like Leana Lovings, it took years of being a cam girl, a few different "audition" sites and now she's gone from being the top requested model in the industry to working the expo circuit and filling roles as background characters. Before her there was Keisha Grey who blew up, couldn't get roles. Went on a crack diet, lost the weight, then had to get implants bc she lost too much weight too fast. Now she can't get roles bc she looks like Skeletor w/ bad, saggy bolt ons.
The MC is definitely on that side where she's not getting roles w/o an existing fanbase. It's certainly a choice the dev made. It definitely doesn't benefit the story or the devs pockets, but there's always a small audience for all types of content. There are 5-600lbs chicks in the industry who wouldn't be able to work any other jobs. Those chicks make me want to vomit, but there are people who find them attractive. It's just a very tiny audience that can only support a handful of such women.