I would blame it on bad form design.
Often personal information like address, city, phone number and email are considered to be standard inputs for forms. It's used because other forms use them too.
When I worked for an ecommerce company I asked them questions about their forms. I asked them why there were two input for phone numbers (optional). They said they phone numbers were required for a certain delivery method. But when I asked why there were two they couldn't answer. They wrote it off as a convention. It's what you do. You ask people for a home phone number and their mobile number.
Fact is there aren't really that much UX experts or people whose knowledge about user friendliness goes beyond "good user experience equals no errors". Especially businesses like gyms, who's core business couldn't be further from UX, don't know that large forms, especially ones asking for seemingly irrelevant information, can scare of customers.