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.
Neurosurgeon doesn't give his/hers content for free, Vice does.
I would like to offer my token of appreciation through one or multiple "tips" when I encounter a FREE video I really liked, same way I do to some other content creators.
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.