(Emphasis mine) So very, very true for almost any US-based private pilot training. Just get 'em past the checkride and all that. Paved runway to paved runway in beautiful weather. The rare confined landing to unchallenging locations. Etc., etc.
The instruction I received during my first private rating was somewhat atypical and I was lucky for it because I didn't know what I didn't know and sure didn't plan it that way. Instead of going to a regular flight school, I had found an airplane (loved that old 150G!) and an independent instructor who was a long time pilot and retired engineer, not a 200 hour, newly-minted CFI. He had me flying in all kinds of intentionally challenging situations: lowering ceilings, rain, winds, moonless nights, and mixed mountainous terrain into all of that. I thought that was how everyone learned until I started my helicopter add-on. For instance, when it was time for the first night dual cross-country I planned what I thought was a relatively unchallenging flight to an easy, well-lighted airport in a rural area. The young instructor was horrified. "We can't fly there", he exclaimed! It turned out he was terrified of, and had no experience in, flying over rural terrain at night. We wound up flying to the big city which might as well have been flying in the daytime. Note--this is not meant to start a discussion of how all rural night flight should be IFR in twins
This truly would have been an easy flight with plenty of horizon reference and I had done it specifically, and many like it, many times in the old 150. It was not launching into inky blackness. But the young instructor sure thought it was because he had no experience in those conditions. I do have to respect his decision, though, and it was the right one given his lack of experience.
Another factor is economic. In airplanes I flew VFR in the rain routinely. The first time helicopter training was cancelled because of rain the answer I got was "Because blade paint is expensive." As an owner I now find this answer to be pretty legit
But it's still an issue.
If you make a request of the school I went to for specific training the chief pilot is always happy to accommodate. Snow. White-outs. Wires. Low ceilings. Whatever. But he's well north of 10K hours. The rank and file instructors are not authorized. Nevertheless I suspect these opportunities are still atypical, which is too bad. They ought to be "typical".
Rotary wing operations beg so much potential complexity that the rotary wing commercial rating is probably more commensurate with the fixed wing private rating than a rotary wing private rating. A rotary wing private certificate is truly just a learner's permit (they all are, but you know what I mean, I hope).