Are Videos On Tube Sites With
 

lets say
yourdomain.com/youporn have permission from owners?
yourdomain.com/pornhub

tnx

Yes those are partnered programs.

so they can be embedded legally on other site?

That's what they want. Legal, likely not, but with tube scrapers you will spend 24/7 DMCA'ing the other sites and will likely get no more then 1% of them taken down.

It is branding the tube. Surfer will remember domain and tube, they will google "domain and tube" and that sponsor just lost another surfer ;) Or just tube search the site. And paysite will see a tiny, tiny fraction of clicks from that.