It's not a hard and fast rule, and I can't lump every juco or transfer into one category. Still, when I see a kid that doesn't work in the classroom or won't stay with their program and compete for playing time, it's a red flag for me. It sometimes means that the kid isn't willing to battle or work for things. If it doesn't come easy, move on to a place where the road might not be as difficult. I tend to picture them in a tough SEC game where it's tight. The team that wants it more, fights hardest will win the game. Transfers and juco players sometimes don't have that drive in them.
Again, I'm not saying it's applicable for every juco or transfer, but I do keep those things in mind when we bring one of those type players into the program. It's a 50/50 deal at best IMO.