davdud101Maybe it the necessary removal processes that really made the analog sound what it was.
There's a lot of truth in that.
An example - a cranked Fuzz Face into a cranked Marshall with the amp inputs jumpered and everything on ten.
Result is a huge amount of hiss and hum because the fuzz takes the incoming background noise, adds it's own noise and massively compresses and amplifies it. Then the Marshall repeats the process. The resulting noise floor is dreadful and, as Pete Cornish puts it, not fit for serious use.
Use a bit more restrained settings on the fuzz and turn the amp down a bit and you can get all the sustain and fuzz out of the setup anyone's likely to need and.... much less hum, hiss and buzz and as a bonus everything's much more managable and more predictable to play into. And that's how it was (and is) done.
The same applies to compressors, even good studio ones. Feed something noisy into a compressor and squash it and the noise floor rockets upwards. So when working in the analogue realm gain staging is crucial and some things have to be avoided simply to keep the noise down.
Vintage studio equipment generally simply couldn't handle modern +4dB levels without instantly and undesirably distorting so levels were kept down to what the gear could handle and that in turn also helped keep the noise down. In modern K-system terminology the levels used were often somewhere around K20 to K14
As for amp sims, I can understand one being noisy if it's "amplifying" an already noisy input chain, but there are some that are so noisy with nothing going into them that if I owned that amp I'd be thinking of trying a valve change in the preamp's gain stage, getting the filter capacitors replaced or trading it in. I have sometimes wondered if the sim programmers simply wanted to add lots more gain to the "simulation" that the real amp is capable of and the noise is a side-effect of that or whether they simply modelled a defective amp :-)