Okay I googled and I found 21 states where yiu can use a 410 or larger to hunt deer. Alabama,Arizona,Arkansas,California,Florida,Idaho,Indiana,Kentucky,
Louisiana,Maine,Massachusetts,Michigan,Minnesota,Missouri,Montana,New hampshire,Ohio,Oregon,Pennsylvania,Tennessee,and Virginia.
New Mexico you can use a 28ga or larger to hunt deer.
I'm not sure how complete this is but 22 states were you can use a 28ga I think would justify ammo makers having a market the brennekes.