I wouldn't say it's a case of lazy upgraders across the board. Some people don't want to spend $300+ for a new board, CPU, memory, etc...The money wasn't a concern for me, just because I have the money doesn't mean I want to spend it. It depends what you do with the system, for me I just wanted a little extra balls for VMs and other stuff and I couldn't justify $300+ for it. Now if you're a big gamer or just like to upgrade often then knock yourself out. I used to do that when I was a gamer, complete upgrade every 3 years, most of that time I was throwing money out of the window.
It all depends how much you can get a Q9550 for, I wouldn't pay ebay prices.
The i3 540 is close in some spots but overall it's slower. You also would be buying a outdated 1156 board to replace a outdated 775 board to run it.
http://www.anandtech.com/bench/Product/143?vs=50