I don't know the real answer since i'm not involved on project like creating a voyeur site 😁
But in my guess is essentially because the money that need to be paid to the tenants to motivate them to be online when compared with the usual incomes in that countries. Also can be in terms of legal issues could be more complicated and comparing with what we know (mainly because of groomy) that is talked by them in this eastern houses, i believe it will be really complicated when everybody will understand the language.
Also believe that most of the audience of this sites already are non - "native" countries (so western side) since normally they are "locked"