Nah, you're totally justified in thinking that way. I hate betting cappers when they're on a hot streak for the exact same reason that you mentioned. They know people are going to buy up their picks like crazy when they're hot, so they will release plays no matter what. They don't want to miss out on money. I really think capping takes a back seat to money in those situations. That's why so many people lose their ass when they jump from hot capper to hot capper.
Personally, my ideal situation is to find a capper who may be struggling at the moment, but has proven to successful over the long term.