When you look up the same value 10 times, you not only pollute the flame graphs and call counts which makes proving that a better algorithm is necessary or has any effect much harder, but more importantly, you could get 3 different states and try to make a bunch of updates based on what should be mutually exclusive states in the system. That's the global shared state problem.

When you look up a value once and remember it throughout a calculation, it may not be the current state, but at least you have a clean snapshot of the data. Which in situations such as cancelling an account immediately after getting one last discount on a purchase, well, we know which scenario the customer probably meant.