i think it's also the ubiquitous nature of particularly, the 318. everybody has one.
stack that with the "devil you know" mentality of: i have a 318 2bbl that runs good, what can i do to make it a little better and not spend 5K? and it quickly becomes apparent why there's so much draw toward the mighty 318.
I also think everyone basically knows/agrees what do to a 340/360 etc.. With 273/318 there's a lot less agreement how to proceed, half the argument is if you should or shouldn't in the first place nevermind what to do if you should.