As far as I can recall, long before the concept of stickiness was introduced for data fields in the Add screen, the Tags field has always been obligatorily sticky by default with no way to turn off its stickiness.
For consistency, Tags should have a pin icon that works the same way as for data fields.
I personally almost never want Tags to be sticky, since I use Anki for languages and add random words that have nothing in common with one another other than being part of some language, but I use different decks rather than tags to distinguish different languages. I can see how perhaps medical students might add a whole batch of vocabulary from one topic at the same time (but maybe they’d use Import to do that instead?)
I think maybe this suggestion was raised in 2021 by someone else, but it’s a bit unclear what the person was asking for, and the results of the discussion were inconclusive.