Yes, the Cluttering of FM is well underway with low power junk, in the name of so-called Diversity. Sad, but largely inconsequential, since only we Radio Geeks care much about how the Airwaves are regulated and even fewer of us who hate LP-FM's interfering with DXing effects of Real Radio Stations.
FM DXing and reception of distant stations is irrelevant to the programming and business models of radio, however. The number of people who listen that way is microscopic.
But the FM band is getting overcrowded, which is why many of us are beating the drum for expansion down to 76 MHz, allowing the move of AM stations to FM, as well as setting aside a sub-band exclusively for LPFM.
FM DX'ing may be irrelevant to people who live in cities, which is about 80% of the US population, but it is way of life to rural listeners who still account for 20% of listeners. They may not know what DX'ing is, never heard of the term, etc. But they put up antennas for TV and FM, and buy radios designed for better reception. Their local mini-Walmart or whatever store may not know what DX is either, but they will know some radios get returned as "defective" and others sell without being returned. So their shelves eventually get stocked with radios that don't get returned - those with better reception.
Format changes force people into becoming DX'ers in a hurry. There are at least two active threads on other boards about classical going away in one city, and jazz going away in another. Those listeners may end up DX'ers if the format is available in a nearby city.
Natural disasters are another way DX'ers are made. Katrina evacuees became DX'ers - listening for any information from home on WWL. I was also surprised to find an active group of DX'ing kids in Lubbock, TX - adept at receiving Radio Disney.
Of course, none of these groups fit into business models. Although Radio Disney in Dallas made at least two trips to Abilene for their DX listeners there. I'm not comfortable with the "local advertiser" argument, though. Most radio ads I hear are for national products or chains. Those ads are as relevant for DX listeners as they are local. A station like WBAP that counts on their large footprint can certainly leverage that fact with advertisers if they wish to do so. A Geico ad, after all, will sell in Olney as easily as it will in Ft. Worth. It is a product people need, and they will buy regardless of where they live. Add the hundreds of little towns together, all of the sudden WBAP has a very valid case to sell to advertisers that their audience is substantially bigger than just Ft. Worth. I bet they can add at least a million to their potential audience - a pretty substantial chunk of audience for national chains and businesses. A Ft. Worth restaurant won't care, but Geico would.