I just thought, seriously, why we pay an edge in online Casinos?
Because almost all the online casinos are coming with player vs gambling-house type of gambling model. Hence obviously gambling houses need some advantage against the gamblers and they are taking it in the name of house edge.
They justify it like they needed it for their running costs coverage. The survival cost could be covered by having some fixed fees. Still we can see no gambling houses are preferring that but they always enforcing house edge against gamblers while playing.
To be honest I do not know how the games could be seen in any other way, in games like dice you are playing against the house, since you are playing under their rules is understandable that they give themselves rules that are favorable to them, the only games where that mentality does not exist is in those games where you are not playing against the house, like poker.