goes back to the analog days when 2-23 was considered lifeline. So as example in Minneapolis suburbs, regardless of who the cable company was at the time (United, then Paragon, Time Warner then Comcast) the UHF stations (17, 23, 29, 45) were always on different stations (13,8,10,12). For a while even KSTC 45 use to say "Channel 45, cable 12" because most of the Mpls area and burbs put it on 12.
With digital I agree they should put it on their actual channel and I know some other companies (newer cable or Telco) do just that. They put the station on that channel and any subs are just sequential. So KSTC45 is 45, MeTv is 46, Antenna is 47 and This is 48 (their 3 subs). This obviously doesn't work where the locals are 2,4,5 and they have 3,1 and 1 subchannel.