One of the main reasons for Juve's poor attendance is Pay per View TV in Italy.
Juve has the most people who subscribe to their matches apparently. I think they make a fair bit of money from this - although I'm not exactly sure how much.
I do agree that 35,000 is too little, against Milan and the bigger CL teams we do get attendances of 60,000 - it would be a shame if we lose the opportunity to have these sort of huge atmospheres.