NDB approaches are still testing material here in the UK, although I doubt they're used much if at all commercially unless you're out in some third world area somewhere. When I did my IMC rating I found them extraordinarily difficult to get my head round initially.
NDBs are far cheaper to maintain compared to VORs, we've seen a decimation of VORs in the UK in recent years.
ADFs (for the uninitiated, the ADF is a radio with a directional antenna used to listen to NDBs between about 190 and 535kHz) are affectionately held in high esteem by pilots in the UK for listening to the cricket on BBC Radio 4 long wave on 198kHz. Occasionally, when there's a live sporting event going on and I hear the result from the cockpit on a plane's PA on a commercial flight, I assume the pilots have been using the ADF to listen to an AM radio station. The AM receiver on the ADF is supposedly only there to positively ident the NDB's AM modulated CW tones, but it's equally at home listening to AM radio transmissions.