Because of the financial agreement with AEG, ie AEG were funding his habits. The current case centres on a uncompleted contract with Conrad Murray, as to who was paying Murray and who knew what.
Basically Michael didn't have a gold lined pot to pee in, until Tom Barrack came along with an eye for investment and stopped the foreclosure of Neverland.
From an article written in the L.A. Times a month before Michael died...
In theory Michael had consolidated all his loans into 'This It Is' but it was AEG that owned the shows and copryright of any footage because they were picking up the tab for Michael's lifestyle.
If you had read MJ's contract with AEG then you'd already know that before MJ could take home any profits from the shows, he had to pay AEG back about $30 million for production costs, a deposit for a house in Las Vegas and the salary for his staff, including Dr Murray. So yes AEG was funding his lifestyle in 2009, but the tab would've fallen back on MJ as soon as the shows started.