This is the problem, but...
what is the solution? Regulators probably without a clue about what they are regulating can create a big mess for sure. Even if they are not pig-ignorant they certainly do not have any nostalgia for this or that aircraft; they are in the business of ensuring some unrealistic level of safety for Joe Public.
There was a famous story about an FAA ramp inspector writing up a Navajo light twin for having "bent propeller tips." Some jokers had pointed him to the aircraft, which happened to be fitted with a new design of prop that was built that way on purpose, when he just whipped out his biro and blazed away with his brain in neutral. It confirmed our opinion of the then-FAA!
We are just peeing into a steady breeze here, given that people in general now expect to be protected from themselves in all regards.
You seriously expect that someone of average intelligence is able to look at an aircraft that is probably more than 60 years old, given that most DC-3s were produced between 1942 and 1945 for use in the Second World War, and fully understand that he is not going to enjoy anything like a modern level of safety? Sad to say, he's been carefully raised, like a battery hen, to go through life not using his native intelligence in that way.
I have been amused by various questions from people I meet when they learn that I am a pilot. The best was a German who asked me why I didn't want to become "a professional pilot." When I asked him what he meant by that he told me perhaps I should think about trying to find a job with Lufthansa.
I just shrugged and told him that meant that I would have to get a licence and all... too much trouble. He shrugged and agreed with that.
How far do you think I could get with someone like that trying to explain the certification standards of 1932 compared to those now in force? About 1.5 sentences into it the poor guy's eyes would roll back to show white.
The DC-3 looks like everyone's favourite uncle, somehow. Slightly shabby but friendly in appearance, who would guess that Uncle has a real mean streak? You could even call him homicidal when treated badly. Lose one engine on takeoff and find, perhaps, that your 65 year-old prop feathering system has pooped out, well, your nostalgia passengers are going to get a lot more than they paid for and never mind whatever you think you can do about that!
I don't much like tourists anyway. To find myself in the front of a -3 with a load of rich ones sat there behind me... I need this in my life? Full marks to someone brave enough to want to do that sort of thing in the face of regulatory opposition; it is an ugly job but someone has to do it. Just not me!