Why do people keep taking OPKs after the 1st positive?

Hi friends! I was wondering what the reason might be for ladies to keep taking ovulation predictors after they get a positive ?? Isn't it just wasting OPKs?? Because if you get 2 in a row, which day do you count as O day?
​I always stop after I get my positive and count the following day as O day. Figured I might be missing something. Thanks!!