About 50 million Xbox Live Users.
Let's assume only 20 Million of them are paying for Xbox Live.
Let's assume all of them pay $50 for it (the cheapest option)
That would equal $1,000,000,000 per year.
Imagine what they could do with that money for their fans instead of just making XBL free.
How many 3rd party exclusives can you get with 1 billion USD? Every single year.
Imagine not having GamePass on your console...