That’s an unrealistic expectation. If they did, it would take a gigantic test matrix and a lot of time.
Who would pay for the testing? Would people complain and rant when their favorite add on from the store was delayed due to a testing backlog? Of course.
Comparing apps in the Google Play or iTunes app stores is apples and oranges and a bad analogy. Those are standalone apps and are being tested on a small universe of hardware/software, and only for the ability to run and not violate certain parameters.
How do you validate that one add on will run with all versions of hardware/software, other add ons, etc.?