Just because "everyone" gets away with something doesn't mean it isn't shabby.
It's in the contract; what precisely is the photographer "getting away" with?
If you plan to show me the pictures before using them, then I plan to approve them once you do. We don't need to sign a carte blanche release in advance for that. And if you'd sit across the table from us and say well then it's going to be 50% more, then I'd suddenly get really sticky about it just on principle.
I will generally tell you which ones, if any I intend to use, but that is a courtesy only.
and just because it's the last thing you want to show doesn't mean some other clown wouldn't decide it's a really cool idea. Or that you won't go nuts in 5 years when your meth habit gets out of control and try to extort my ex-bride and her wealthy new husband (after all, I'm far to principled to ever make any real money, so it's only a matter of time before she comes to her senses and leaves me).
If you think it's worth 50% more to not be able to use my pictures, honestly, unless your work was so much more compelling than what other people are producing for the same money, I'm going to take a pass. every. single. time. Take out a pen, strike out the clause and initial it. I guarantee you that if you won't, I'll find another equally talented, priced and available photographer who will.
The simple fact is, if you are going to be "principled" about my potentially using your images in portfolio, I am going to chalk you up as trouble, at which point I pull out a list of other local photographers and say, "I don't think I'm going to be able to provide what you need for your event. May I suggest you call X, Y, or Z?"