Not having Mode C is a cost issue, at least usually in my experience: most of the planes I fly (rented) have had Mode C fitted in the past, then the encoder has gone u/s and as it's not essential for a C of A renewal, cash-strapped FTO's don't repair it.
Doing my IMC rating recently was (this will probably horrify the ATCOs out there!) the first time I had ever flown with 2 VORs, ILS or DME: the plane I usually fly has only 1 VOR, no ILS (even LLZs don't seem to work), and a very nice vintage ADF. Oh, and GPS, but of course I'm not allowed to use that to navigate with...
Tim