But.
A mattress isn't a trivial purchase (not just in cost, which is what you're disrupting, but in what it does for you). You use a mattress for a large period of your life and it has a great effect on your health (either good or bad).
Being able to physically lie on a mattress in a store provides some value in regards to feeling how hard the mattress is, how it responds to your moving around, etc.
I'm not sure I could buy a mattress online sight unseen and just "hope" it was the one for me (and my wife), hoping I didn't have to deal with returns, etc. (How the hell would I return a mattress via UPS/FedEx?)
Maybe I'm overthinking it?