At the start of digital broadcasting, TV stations where broadcasting both analog and digital channels. For most markets there was no room on the VHF band so the digital channels were broadcast on UHF. Virtually all the digital broadcasts were on UHF channels so antenna manufactures started pumping out UHF only antennas and calling them "Digital Antennas".
When the analog broadcasts were shut down, this freed up most of the VHF channels. Many stations then moved their UHF digital broadcast down to VHF. About 25% of the stations in the US are now broadcasting on the VHF band. Virtually all are on high VHF channels but there are a small number on low VHF. The government is in the process of auctioning off another chunk of the UHF band so more stations are likely to move down to VHF.
When shopping for a TV antenna it is best to look for one that performs well for both VHF and UHF. The Winegard Sensar IV is about the only RV antenna that does this.