Who's going to pay for that? Not only the software, but the video hosting, transcoding, etc.
And don't tell me you can do it with p2p - the entire point of tiktok is that you can load new videos by swiping your finger. If every video takes 10 seconds to begin buffering nobody will want to use your app.
I heard these same arguments about the Linux kernel, back in the days before it came along and ate everyones' lunch.
This app can be built, quite easily, by anyone motivated to do so. Just like the kernel, just like a distribution vendor, just like any one of the thousands of highly successful open source, community-oriented projects out there.
And don't tell me you can do it with p2p - the entire point of tiktok is that you can load new videos by swiping your finger. If every video takes 10 seconds to begin buffering nobody will want to use your app.