Yeah I agree, the whole purpose of a membership is to be able to go whenever you want :/
ZSL actively market that as the primary benefit, and in certain circumstances a membership could generate more income for ZSL than from that same person’s visits as a non-member.
Somebody who’s at either zoo on a regular basis is more likely to recommend it to others, or purchase food and drink, or purchase items at the gift shop.
Some people could argue that the memberships are a bit too generous in regards to the unlimited visits for the year, but all those visits are fresh opportunities for ZSL to profit via the other methods.
Fun Fact: In ZSL Membership’s original iteration,
Lifewatch, it
only covered London Zoo. That being said, you got two vouchers for half-price entry to Whipsnade/half-price guest entry to London, the latter of which is one of the few benefits no current ZSL Memberships include.