My guess? Possible Spyware, that's why. Information gathering's nothing new for any country (especially in the USA), but due to antics going on that could cause possible danger instead of just "encroaching advertising".
(Though, if it IS because of how many members embarrass the POTUS to ends that makes Twitter blush, then... wow, haha.)
If Tik Tok gets banned though, webcomics tied to foreign markets could be a problem... and we'd have a Vine 2.0 situation with all of those influencers invading YouTube. And boy... its only been 7 years, and I ain't ready for that shit again.