Probably because they are a for profit corporation, not a charity. So the same reason why there’s not a tip jar in your neurosurgeon’s office and no donate button on AP videos.
Vice’s business model doesn’t run on tips, it runs on ads and YouTube revenue split.
That’s nice that you want to tip a huge corporation but it seems that you are rare enough that Vice hasn’t found it meaningful enough to add a tip method.
Personally, seeing a tip jar on a “news” organization’s content would be about as welcome as seeing a tip dialog at my dentist office.