It is obvious that it could be and has been done on every other ATSC tuning device in the free world, but I think there was a method to their madness which will carry forward. I believe that scanning is a feature that could be added to the HR20 if they chose, but I think they've unfortunately and decidedly chosen not to.
For all of those who say it doesn't matter, you're selfish. It matters to everyone who is not served HD LIL at all or is partially served to the exclusion of one or more major networks. The way things are going, even if DIRECTV is set up for 100% coverage of those capable of seeing all of their birds, if they don't solve the issues with LIN and others who can't come to an agreement, quite a few will be shut out of at least one digital channel.