I'd like you to dig a ditch for me...
Oh, and you have to use this garden spade...
Oh, and the handle is made out of jelly...
Oh, and the ditch is on the beach so the tide will be coming in any time now.
Hyperbole, yes. Web development isn't exactly ditch digging, but if you really want to understand why so many web developers are openly hostile toward supporting these older browsers, it's because the exercise is tantamount to digging ditches with jelly-handled garden spades on a rigid time table. When you get in to these much, much older browsers, it's a back and forth game of break/fix whack-a-mole. It's broken in one browser, so you try to fix it by using another approach, only to find that it's now broken in the current browser. That or you end up using ugly work arounds that just cruft up the application and make maintenance a nightmare.
Ultimately this comes down to a business decision. I consider each browser version as a market to be sold in to. I may find it an unrealistic business proposition to increase my developer hours by 30%, just to support a specific browser, when there's a big fat market of current browser users ready to use my application.