OT Zap2it changes with the times?

I used to use Zap2it TV listings a lot. They have a setting for each
cable or satellite company that operates here and a setting for Antenna,
which is what I use. But when I got a better antenna and an antenna
amp, and I could get DC stations, it was a problem because the listing I
was using only gave Batlimore stations. No easy way to have it remember
2 zipcodes at the same time, so I got a zipcode map and tried zipcodes
half way between Balt. and Washington. I thought I'd only have to try
one, but the first 4 didn't work. One didn't have Balt. or DC iirc
But I found one and used it for a year or two.

Well, I don't remember what it was, but this time when I put my
Baltimore zipcode in, it has all the DC stations too.

I wonder how that happened. Was there a wave of people getting better
antennas? Or did they do it just for me?