Probably because of the acidic juices burning holes into our anal area. Just my guess. And then fistulas can develop. My surgeon said people who eat a lot of acidic and spicy food are more likelier to develop an abcess than those who eat a blander diet.

Does that make sense 

I don't think spicy food has anything to do with it. We have a few reasons to be more prone to peri-anal abscesses: 1) we have an ulcerative disease, and any one of those ulcers can get out of control, 2) we have had surgery in the area, and surgical sites don't always heal as we'd like them to, and 3) some of us have undiagnosed Crohn's disease.

I suddenly developed an abscess with a fistula last December.  I do not have inflammatory bowel disease.  It took 4 admissions to hospital and 7 ER visits to get the little devil under control.  I still have one that is constantly there and I will deal with it when I get back from my beach holiday!

My surgeon has no idea why I have developed this problem.  I do know that when I take care of myself (good diet, enough sleep, control stress) things get a little bit better.