Because Google and Apple are private entities, and they're not beholden to the government's whims. They have relationships with citizens, who may not necessaril

Because Google and Apple are private entities, and they're not beholden to the government's whims. They have relationships with citizens, who may not necessarily agree with the governments' assertions. And because the government is forced to follow a set of rules for enacting laws. Talk isn't enough to enforce will. I think a better question to ask is, under what authority is the US government talking about banning TikTok? If there are clear security issues, or TikTok or the people running it are in violation of some US law, the onus is on the government to prove it. I haven't seen any proof of this, just a lot of hearsay.