Many AM stations that were once a music format back in the 80's are now news/talk. When you talk, who cares if it's mono or stereo.
From what I understand, various remaining AM stations that flicked off the stereo signal, while still maintaining some form of music format decided that it's actually better to stay mono, broadcasting with music that was originally recorded in mono anyway.
Even talk stations could benefit from stereo. The bumper music, promos, commercials etc really sound nice. I heard a number of news/talk stations in stereo some years ago. The two that come to mind are WJR in Detroit and KMOX in St. Louis. They had promos which were produced to "show off" the stereo. One in particular I remember was on KMOX for the Cardinals. Crack of the bat out of one side, crowd roaring on the other side. Sounded awesome. And that was listening at night to the skywave signal. Probably sounded even better local. On the music stations...I'm guessing that more than 50% of the music played on 1050-CHUM and 1150-CKOC is in stereo. Maybe someone from one of those stations will read this and tell us. Both used to be in stereo, but now are in glorious mono. I can see why a company today might not want to invest in AM-Stereo (though I'd invest in that before I would the IBAC crap in the US) if you're doing news/talk, but I cannot understand why you wouldn't use it if you already have it. On a music formatted station, I would definitely do stereo. Like I say, a lot of cars out there have it...and when you tune in a station in stereo, it really jumps out at you. CFCO is a great example. I think CHUM and CKOC should turn it back on and CHWO should get it. And I even think CJCL, CFMJ, CFTR, CHML, CFRB etc should turn theirs back on. What's the harm? Oh well...that's my opinion. And worth what you paid for it.