They might have changed radio shops they do business with. Who knows.
It's probably a good thing they changed to DPL. PL 179.9 and 173.8 are both screamers of PL tones where they are easily heard as they "sing" and can be annoying.
PL 179.9 is a poor choice of PL to begin with because it is the 3rd harmonic of 60 Hz (180.0 Hz) and could get false decoded by any noise or other signal having 60 Hz AC line hum on it. PL118.8 is also one to avoid because of it being close to 120.0 Hz, the 2nd harmonic of 60 Hz. PL118.8 would often get false decoded by TV sync buzz back in the days of NTSC analog TV.
I use DPL (DCS) on GMRS and MURS. DPL also stands for "Definitely Prevents Losers".