At the speed web development is moving, I don't see much sense in coddling browsers that are more than 2-3 years old.
If you are, great. No coddling necessary. But for other people, they may not be comfortable with the percentages yet, and I think that's perfectly understandable.
Coincidentally, I work in the multi-family housing industry, and one of the industry titans requires IE to use their product--which everyone uses--so we have ~82% IE share on our own product (which is supplementary to the titan). Of that, IE8 stands at ~31% of our total site traffic, which is compelling enough for our company to need to support it. (IE9 is only ~39%, with IE6/7/10 making up the remaining 12%.)
So until that industry titan changes their way, we're stuck in an IE rut.
Far more so than that, though, what's shitty about having to support IE 6-8 is the complete lack of consistency. Even if you aren't doing anything fancy, you have to spend a hell of a lot of dev time if you want things to look the same across browsers when they're included. Hours and hours of wasted time is pretty shitty, especially when the work involved is so aggravating and, from a creative point of view, utterly pointless.
In effect, your question is like asking what would be shitty about developing apps for a 10-year-old Palm Pilot. There are millions of use-cases perfectly covered by those too, but that doesn't mean an iPhone app developer is going to want to spend time porting his apps to one.
Secondly, you don't have to design 1:1 pixel-perfect copy of your website that looks the same on all browsers.
The main thing - if your developers cannot degrade the website functionality - they are seriously doing something wrong - get more experienced
You can as well design Flash site and call it "progress" and tell the rest of our users to go somewhere else. Now, how is it different from other "modern" technologies? Its W3C support?
"but that doesn't mean an iPhone app developer is going to want to spend time porting his apps to one."
If your customers still use Palm Pilot, then why would you design your site ONLY FOR IPHONE??????
If your customers still use Palm Pilot, you've chosen the wrong market segment. Yes, make something people want, but you're allowed to be selective about who those people are. If you're a hacker, it's very likely because you enjoy creating and working on interesting and fun things. Making websites work in IE6 is not a fun thing. There is enough value waiting to be created that we don't have to waste our talents and energy on this kind of nonsense.
And if you don't develop cross-platform because of lack of time this is fine. Please, don't cover it with insults about dumb CEOs and ignorant lame users - bad excuse for bad programming habits (not personal, just generalisation).
Again, there is no technical reason not to give workable version of the website to all major browser users. It doesn't have to be a pixel-perfect copy. It just has to work.
I didn't insult anyone, CEOs or users, so your generalization is a very poor one.
The technical reason for not giving a workable version to IE6 is that it can take as long to make a workable version for IE6 as for all other browsers combined. IE8 is not that bad, but it's similar in principle. If I have to spend 50% of my time on 10% of my users, I'm better off doing twice as much for the other 90%.
Does someone have a gun the CEO's head stopping him? He could tell everyone to install latest Chrome or Firefox and have everyone upgraded in 10 minutes.