Usually seedless variants of fruits loose more then just their seeds - at least in my experience they tend to loose also a lot of character and depth.
Since mangos are much less "pick up and eat" compared to, say, grapes or even water melons I'm not sure if there would be that much demand for a type of mango that might be somewhat easier to work with but is of a (presumably) lesser quality. If you want a hassle-free mango and do not care too much about quality canned mangos are an already existing option.