The reason you have to put digital tuners in sets is because this is a Govt mandated complete switchover of OTA tv. This isnt a case of simply letting the market decide. If you did that you'd have to run the analog side of things indefinitely (since theres so many people that'd never otherwise buy in) and if you were going to do that, the last thing you'd have done is have stations begin transmitting in digital in the first place.
As far as copy protection and tuners go, uh, they dont really have alot ot do with each other. The first thing you have to be able to do is simply tune the channels. What happens *after* that is up for copy protection. In other words, think of all the sets out there, particularly the smaller ones that dont have any video outputs to begin with, only inputs. Obviously theres no copy protection issue there because you can, or could, in the case of a digital tuner, view the signal.. and nothing more.
As far as actually implementing copy protection on devices that do have digital video outputs, thats another matter. Tv's with digital tuners (or STB's with them) can still have the usual old outputs (s-video composite whatever) just as always. But they'll also have a firewire output to send to digital VCR's that does have copy protection (copy never <heaven forbid>, copy once, copy always etc) built in for taping considerations of the supposedly primo content.
Point being a person can rant and rave about whether we even needed to switch to digital OTA anyway and thus the need to now incorporate tuners.... and/or they can rant and rave about copy protection of certain digital content but the 2 issues arent really one in the same.