Unfortunately a number of thrift shops closed their dressing rooms during or after COVID-19.
Some have kept them closed as patrons have swapped the clothes they wore into the store with ones from the racks. Others poop or leave all kinds of trash, including soiled diapers, in the dressing rooms. Piles of clothes people try on were also left in the dressing rooms. These were all reasons why some thrift shops no longer have dressing rooms, although they keep their customer bathrooms open.
But some still have dressing rooms.