I'd never play MP in a Bioshock game but I still don't consider it to be something worth gloating about. Not having multi means they either couldn't get it working in time or didn't have the resources to dedicate. I don't think any developer has ever made the decision 'we could do multiplayer but it would take away from SP'. In the end the product is just less fully featured than it could've been (regardless of whether I would even use those cut feature(s)).