Even though the major networks are showing most of their primetime programs in HD, not all local affiliate stations are passing the signal on.

Some stations simply choose not to, while others either have not yet upgraded or don't yet have the budget to do so. Replacing all that HD equipment with new HD devices can be very expensive (some stations have paid millions to do so). While some of those stations that haven't yet budgeted for it, they may eventually. Those that choose not to may never upgrade their broadcasts. Because the digital transition only requires a station to switch to a digital broadcast, not transmit HD, they aren't obligated to.

Even some stations that do broadcast an HD signal also broadcast additional extra channels (known as sub-channels) in their broadcast signal. Because these additional channels take up part of the space HD needs to look its best, it can cause HD video to degrade. This process (called multi-casting) allows stations to air other programming on multiple subchannels. This can be a weather radar, additional news programming, infomercials or anything else a station thinks might draw viewers or generate revenue.