I don't disagree in general with what is said above (thank you Ally by the way!
). I've hosted and am happy to host all within the regulations applying at the Club concerned.
Long-term tradition, standard of the course and tee-time availability also have quite a part to play.
At some clubs I've observed from a distance quite a few instances of 'iffyness' between members and their non-member mates and business contacts which does contribute to ill feeling within the rest of the Club (eg "I see Tom/Dick/Harry is playing with his non-member next door member yet again today"). Matters can also be awkward for pro-shop etc staff when say a member attempting to take excess-advantage of a guest arrangement also happens to be a committee member!
Things have likely changed a bit over the last few decades though. Not only with travelling golfers, arranged group parties, societies etc etc but also because there are now, at least in the UK, a significant number of Open Comps at most, but not all, private members clubs. These permit players with official hcps to play other courses at lower than standard green-fee prices.
One area where there is yet to be consistency though is County Card and Golf Union arrangements, ie Eng, Scot, Wales, NI or RoI County Cards or equivalent are not valid in other parts of E/S/W/NI/RoI.
Lots of food for thought.
atb