It's that phrase in the OP "choose not to eat meat for a variety of reasons". If the reason is not liking to chow down on gobbets of flesh they may not object to things like chicken stock, fish sauce, Worcester sauce, anchovy essence etc. and the chef wouldn't to have to guard against any possible 'contamination' with meat/fish essence as though customers were going to go into anaphylactic shock if they inhaled a speck of oxo (even to the point of making sure one didn't use the same spoon/pan). Perhaps predominantly vegetarian dishes are much easier to attain than strictly 100% vegan dishes? Though when the Blue Brick cafe stopped doing bacon and sausages at breakfast time I just sucked it up and went elsewhere.