I'm an App Developer who has never done this. Every app developer I know has never done this. I really don't understand why you are so bitter for absolutely no reason, except maybe you have a 3GS and won't upgrade.
A quick search will bring up tables of which device requirements will disallow which devices, so it's not an unheard of practice. But nobody is excluding potential customers out of spite, it's because the older harware genuinely can't handle the apps.
I have a 3Gs so i can also be exception, like you, and keep upgrading my apps/sites and not having to add "front facing camera" just so i can be a slob and not test for the phone poor people uses.
screw upgrading phone every year. my gaming desktop is not upgraded that often.