To add to other comments here, new Nintendo games were supposed to be more expensive physically - say, $80 instead of digital $70 for the new FE - but it turns out, retailers don't want to be undercut by digital sales. So at least at launch and for some time, the physical price is slightly less than physical, so people want to buy them more. (I assume Nintendo asked for more money to provide physicals though, so the retailers get ~10 bucks less per sale)
Remember that retailers with an unsold copy lost money on it, while Nintendo loses nothing from not getting a digital sale (though they still prefer selling digital, so they get all of the money)