I am always surprised when people use someone else’s private property for some kind of commercial gain without their permission because they figure they will never know anyways. If they find out they will simply ask for forgiveness after. Some examples could be photographers who want a great backdrop for their client and so they essentially try to get a quick photo with their client on the property where hopefully the owner has no clue and they walk away with a great photo with their client in it.
That fact that I hear people having this as part of a regular way of doing business is strange. Imagine advertising in a brochure that you could bring a paying customer to a specific location that you have no rights or permission to access. In some ways it’s like renting a room out for a house that you don’t even have any association with but hope the owner never finds out as you make money from it. You may think that is rare but it seems to happen quite often.
The strangest thing is when these types of people contract professionals to do a specific tasks where once they arrive on site they do their job but are oblivious that not everything is legit I guess you could say. For example, imagine someone hosting a party on a property that’s not permitted and they hire people to DJ for them. At the end of the day the contractor should still get paid but I guess that’s why at times you should also make sure that the people hiring you are doing everything professionally as well.