A membership shared between two people, a card handed to a friend for a single visit, a family membership stretched further than it should be. None of it shows up as theft, but it adds up to real lost revenue over a year.
A photo printed directly onto a membership card is the simplest deterrent there is. It doesn't require new technology to be installed, just a card that makes it obvious, at a glance, when the person presenting it isn't the person pictured on it.
Paired with access control readers logging every entry, you also get a record of usage patterns per membership, useful for spotting a card being used at times or frequencies that don't match one person's visits. It also means your usage data like, class attendance, peak-time patterns and capacity planning, reflects who's walking through the door, not just how many cards were scanned.
It's a small change to the card itself, but for a membership-based business, it's one of the few decisions that pays for itself directly.