It's pretty simple that they are not use to it like us... Infact it all started with hindi tv channels... Such as Setmax, stargold, zee cinema use to telecast south hindi dub films every week.. Then the trend of youtube channel begins.. You can calculate a youtube channel Goldmines telefilms has more then 60million subscribers which show show south movie in hindi dubbed versions.
And there is no such tv channels or youtube channels in south that telecast hindi movies in south dubbed languages... And there are so many small, medium level so called youtube reviewers who use to watch, review and promote south films as indian films and ask their subscribers to watch and support those films.
But what i think is slowly slowly they will begin to show hindi films as well.. Its only a matter of time..