Because Microsoft, Apple, and Google are free to host whatever software they want. So make them not want to host TikTok. They can just come up with some BS as to why they don't host TikTok. The BS doesn't even have to use the words "China" or "Chinese" as long as the BS can conceivably be argued to include TikTok but not Instagram and whatever else you have. Doesn't matter how stupid the BS would be ("Ah, we don't host social network apps that starts with the letter 'T' unless the next letter is 'w' so Twitter is ok but not TikTok") because it would be understood by all that it is BS.