>>30196262Honest reason - it makes no business sense for them to do so. While brand awareness isn't as big an issue for TPCi as is for other companies, the existence of Showdown is good for Pokemon as it promotes brand engagement (keeps people engaged with Pokemon in some capacity) and brings back players who might otherwise have stopped playing.
On the flip side, even though taking showdown down is perfectly legal and within their rights, in addition to the outcry from the community (which is a big deal, but not overly so), they lose the brand engagement that they had as Showdown players might end up going off to play Hearthstone or some other game instead, not even thinking about Pokemon. Best case scenario, some other simulator pops up, probably downloadable and decentralized like Pokemon Online. However, it will necessarily be harder to access than Showdown.