After leaving the RAF I briefly flew an Aztec, part based at a grass field in the NE of England. The pundit was a home made perspex box containing a jumble of recycled green discharge tubes.
They also enterprisingly operated an MF transmitter, into the legality of which I refrained from prying. Together with cross cuts from a conveniently located VOR it made a very decent approach aid which, of course, I never used whilst on public transport operations.
What am I getting at? Well whilst the NDB has its limits, of which all instrument rated pilots should be aware, it is a cheap and easy navaid to install and use.
I must say, when I started flying a few years ago I thought that, by the turn of the century, NDBs and HF radio would be things of the past.