That's not entirely accurate - TikTok does have a JS "pixel" implementation that website owners put on their site, mainly to track conversions. It's true that the use case makes it less popular than a like / share button. I research these JS snippets and how they work, and I can say that without a doubt the TikTok pixel is the most complex and network intensive one. It without doubt collects a lot of information. As more advertisers move to TikTok, i see this pixel implemented in more and more websites.