Ostensibly it's to pay for staff and the various equiptment/facilities that staff would use. Government doesn't happen by magic or for free. In fact, it's very expensive.
What has happened is that Congress has refused to give the Biden team any money to do any of the transition prep work, which Congress doesn't have to do until Trump either concedes or until Congress formally certifies the Election; but the Democrats and Lugenpresse want to pretend that it'll take three whole months to get Biden's team up to speed and that any time between November 3rd and Janurary 21st not spent on setting up a Biden presidency will cause millions of deaths or something.
The reality is that most of the government doesn't give a shit who exactly is the President. It's like the Government Shutdown. Remember that? Congress says no more money, so what does the Government do? It... uhh... keeps going. Because it doesn't really care if Congress says no, or if the President is fighting with Congress. The country functions with or without any given politician's approval - for better or for worse. But Biden right now isn't part of the government, and it's important that Trump keeps him out because once the Biden team establishes themselves, forcing them out of various clearances and automatic fundings will be difficult.
