Don't be like that. They had a good reason. The iPad is also different to the 3GS - One's a phone, the other a tablet. It could all be because apps are getting so much better for the iPad that they didn't want stability issues to happen since memory usage has increased. Probably iOS6 takes more resources too.
On the other hand, people using a 3GS won't probably use it for nothing more than social networking, pictures, and productivity apps.
I for one will not be sad about that. My 1st gen iPad has been getting slower and slower with each update, to the point that I don't even install them anymore.
iPhone 3GS is still on sale, and I'm sure Apple doesn't want people who own what is technically a brand-new device to complain that they can't update to the latest software.