A lot of people in the area were slowly turning into pigs. It had become such a ubiquitous occurrence that quite a few people were moving past fear and horror into a begrudging acceptance...after all, it was hard to be judgmental when you or any of your friends or relatives could be next.
Besides the obvious physical changes, there were some mental ones as well, including a desire for less clothing. Pigs have fewer sweat glands - it's why they tend to roll in mud to keep cool - and clothes became uncomfortable in the summer, if they even fit at all anymore.
When the owner of Gino's started going piggish himself, he decided to make Monday nights "pigs only," creating a judgement-free zone where those slipping into hogdom could relax and enjoy a nice meal comfortably. It became a sort of support group, and as their numbers swelled along with their bellies, he considered setting aside more evenings, or even going exclusive.