Because as there are more and more people involved it becomes more complex to accommodate everybody. I'm having the same problem this year. I'm waiting to find out what my son and his fiancee are doing in order to tell my sister and my mom, in order for them to get back to me in order to set up our plans, so that we can include them in to our celebration without them having to miss out on her family's celebration(s).
I spend every Christmas alone. I have no idea what you are talking about.