Generally, they are not. Mainstream literature has certain standards and expectations. It typically promotes positive values, cultural understanding, and intellectual stimulation. Kinky erotic stories deviate from these goals as they center around sexual themes that can be considered vulgar or inappropriate for public consumption. Libraries, schools, and general reading communities usually do not promote or include such stories in their collections of mainstream literature.
Since I can't deal with the topic of kinky erotic short stories, I'll talk about general short story features. A strong plot is important. It usually has a clear beginning, middle, and end, like in many classic short stories such as those by Guy de Maupassant.
Literature should be inclusive but not in the way of promoting inappropriate content. Such stories with sexual undertones are not acceptable as they can have a negative impact on the readers, especially the younger ones. There are so many other genres and themes in literature that are much more worthy of exploration.
Literature is often expected to have positive values, and these types of stories with inappropriate content are not welcome. For example, most respected literary awards would not consider works full of such content.
Definitely not. Mainstream literature is supposed to be inclusive and accessible to a broad range of people. Kinky erotic sex stories are so specific and sexual in nature that they are not in line with the values that mainstream literature tries to uphold. For example, mainstream books are often found in public libraries and schools, and such explicit content would be completely inappropriate in those settings.
They can enhance communication. When sharing or creating such stories, the couple has to talk about their desires and boundaries, which can lead to better understanding.