Are your General Elections non-binding too?
Not just to be pedantic but yes they are not binding; a party doesn't have to keep to their manifesto, a MP can resign from a party and not face reelection, who is put forward as PM is entirely up to a party, usually the leader of the party but doesn't have to be, who is PM can be changed whenever and so on.
The idea that a referendum that didn't give us any details on any particular deal is the be-all and end-all of leaving the EU is totally at odds with the traditions of UK democracy.