for example, cost, might be one reason. The bandwidth cost you money. The more people use it, the more money you spend. Like running a gym, you want everybody to have a membership, but You don't want them to actually come to the gym to avoid paying for utilities.
Similarly, recently zoom said their quarterly income will be lower, because they need to invest into infrastructures due to increased usage. You would assume, the more users they have, the more money they make. not necessarily.
Also to ensure better streaming quality and availability, the media files have to move to server closer to the client region, depending on trending demands and timezone usage to avoid bottleneck at the delivery stage. Storage is also not a free resource (or server renting space)