I'm sure there's some way to use a nonsexual npc so that it makes sense, but generally the more interaction you're forced to have with them the more I hate them. it's drivel to skip on your way to the fuckable npcs.
technically, it shouldn't be like that, but once you know there's other storylines leading to sex it's almost impossible to get interested in any other kind of storylines. this is the core problem of porn with plot, the sex interest takes over.