I totally agree, when I'm playing offline and need to attend to something urgent I expect hitting the options button, or even the PS button to pause the game.
I cannot believe such an oversight made it to the release build of the game. Do none of the developers or testers have a life outside of the little bubble they are in when developing the games that causes any kind of interruption when they play.
It's a total pita to have to do the same thing over and over because you have to leave the game for one reason or another, only to discover you've been busted because the game keeps going in your absence.