It's all about comfort level.
For me, I'm not interested in a lot of rebuilding. So I'm not going to do a lot of trading for prospects. So I don't need ADV to judge YOUR prospects. I know how much I spend on prospect scouting. I know how I develop players. So I don't need ADV to evaluate MY prospects. So why would I need ADV?
For others, they're always trading for young players. So, if you're doing that, you have to know how much your trade partner spends on prospects scouting AND know he uses it well. If he's willing to deal a HOT PROSPECT, did he screw one up? And, if you're trading for 3rd year players, you need to know how your trade partner develops players. This person needs ADV(in my opinion).