According to our real estate broker, exclusivity clauses are common among specialized service businesses, and less common among small shops and restaurants.
We wanted to move into a certain spot here in our town, but it was technically part of the same shopping complex that one of our competitors was in (it kind of zig zags around with multiple different buildings), and that competitor had an exclusivity clause. So even though they had multiple open spots, and were looking for tenants, and we wanted to rent from them, we couldn't. This same shopping complex has 2 phone stores and 2 hair salons, so I didn't think it would be an issue, but.... it was.
It probably depends party on supply and demand. At the time that that competitor moved there, he was the only martial arts school in town and had been in business for years, so he probably had a strong negotiating position to demand that clause. Hair salons, on the other hand, are a dime a dozen, so the landlord was probably in a position to go "if you demand that, I'll just get a different salon".