If the site does have less player then expected those pvp duels wont be a hit because no one would able to duel against players and that's a major problem among newly built website but if its placed on an old reputable site then it might a hit and profitable just like on Bitdouble.io they do have coin flip duel (player vs. player) its still new but there are lots of player do play. Adding vs. house should be always there just like other common gambling sites.