I have always found that amusing; people who trash Canon at every turn then go buy an adapter and use nothing but Canon lenses on their Sony bodies. I do think the RF mount hurts Canon as well though, sure there's an adapter but with RF lenses costing more than their EF equivalents, and the fact that the new bodies aren't native to the EF mount; these factors can't help but slow adoption.
The larger sites yes (especially Amazon), but you might be surprised at how many smaller sites still don't collect taxes. Even B&H didn't collect taxes on my recent purchase. It's really based on the state the company is in, the local laws of that state, and the laws of the state that you reside in.