What’s stopping people from forming their own group for content?

When I want to do my daily fractals or strikes and see nothing in LFG, I just create a group in LFG. They usually fill pretty quickly and most people are nice and knowledgeable of the fights. Sometimes I have to wait a bit for the group to fill so I just do something else in the meantime or post on lfg in another time. So, what’s stopping people from forming their own group, especially when they are experienced themselves and the content is relatively easy.