All kinds of relationships can be hard work. They wouldn't be as rewarding if that wasn't the case. At the same time, there is a difference between exercising healthy boundaries and just making things difficult for the sake of it.
Unfortunately, many people don't seem to think that this applies to heterosexual dating etiquette. It can often be a strange adjustment when a single friend starts dating someone, but I would have thought the priority would be to make everyone involved as comfortable as possible (so long as they aren't going out with a douchebag).
This appears not to be the case, as one Twitter user sparked a heated conversation with the claim that she goes out of her way to avoid befriending the boyfriends of her friends. While some wholeheartedly agreed with this principle, others were not afraid to criticize it as weird. If your friend doesn't trust you around the people they care about, why are you friends in the first place?