Card Counting

Hey guys- I live next to a small casino that seems to be much less "serious" about security than the huge casinos in places like Vegas, and I am toying with the idea of practicing card counting. This may be a dumb question, but I'm wondering why it is not sufficient to only keep track of the high cards? They use a 6 deck shoot. Let's say we are 3 decks in, and I've counted 85 high cards so far. With 25 high cards per deck, I know that 10 more have been played than average. AKA, I know the relative proportion of high cards to low cards without keeping track of every card. I'm aware that there is estimation being done here, but you also have to estimate the amount of decks burnt to get the true count in regular card counting. It just seems to me that it would be much much easier to only keep track of the high cards. Thanks!