I don't know about you, but I don't buy something in every shop I go in. I've been known to browse casually and then walk out with no purchases as there's just nothing I want to buy.
Why then do I feel awkward about walking in a pub and walking out again without buying a drink? I've browsed the pumpclips, and seen nothing I fancy (or even like in some circumstances), so left to seek out a hostelry with better options. There really shouldn't be a compulsion to stay and spend, but it is the norm so to do.
I wonder if you are a common pub-browser, or, perhaps more interestingly, if you work in a pub and see someone walk in, look at the beers, and walk out again, what do you make of them?