If I quit running the inn, I think the diet hassle be the main reason why.
I serve a pretty traditional American breakfast. Everything is home baked.
We have a couple of gluten-free items: waffles (rice, corn, oat), blueberry muffins, and French apple cake. Always available and always tasty.
Dairy free – lactose – can be a little bit more of a problem, but I can work around it.
Vegetarian, never a problem – meat is not a part of anything, it's always on the side.
If you don't like eggs, I can manage something tasty for a day or two.
Vegan... We always have fruit and home-baked bread is vegan. But I figure if you're vegan, you're not used to having an elaborate meal and since your breakfast must be individually prepared out of a larger group and served at the same time, I can't make it too fancy and don't try.
Where I have a problem is when you stack up requirements: no eggs and no dairy, gluten-free and vegan.
And of course, where it goes off the rails is where someone declares a dietary requirement and then is able to bypass it at will.
I was preparing special breakfasts for a woman with a dairy allergy, and I see her putting half-and-half in her coffee. I warned her, that is not a nondairy creamer. She says, oh I can have a little bit dairy. But she was telling me no butter no hint of dairy in anything, so, argh.
A while back, a gentleman in a large family group, which booked the whole inn for the weekend, declared he was "gluten-free and vegan". Okay. I serve breakfast to him: a bowl of steamed jasmine rice with sliced strawberries on top. He enjoyed it and then I saw him sneaking a sausage from the buffet. I made a finger pistol, pointed at him and mouthed "busted". From then on, he ate what everybody else ate.
And it can work the other way too. Two weeks ago, I had a older guy (retired) and his son on a fishing trip arranged by the older guy's wife; she didn't come. When the two gentlemen arrived, I inquired about breakfast. The son informed me that his dad was supposed to be vegan. His dad interrupted, saying that he didn't want to put me out making anything special and a couple of eggs over easy and sausages would be just fine. They were here a week and on their last morning I fixed the vegan breakfast: home-baked high-fiber bread with avocado and almond butter as a spread and lots of fruit. They needed a light breakfast because they were going to be sitting in a plane for 10 hours and I told him that they could go home and tell the mom that "it was a nice B&B and they served a vegan breakfast". Maybe just once, however.