Other equipment like spectrum analyzers, VNAs, scopes, etc. are now way more accessible, but they seem way less complex.
I'm with you in wishing that they were more accessible, though. So many people want to do skydives, bungee jumps etc. that have never experienced the thrill of exploring the anatomy of tiny insects in incredible detail. They don't know what they're missing! That's before you even get onto cool stuff like WDS/WDX which I remember thinking was like science fiction when I first saw it.
LN2 costs like $1/liter-- it's cheap.
It’s the appropriate container, handling equipment, PPE, and safety technique.
Unfortunately, as some of these things get cheaper you start attracting a different level of hobbyist who are less interested in learning proper handling technique and safety precautions. Not all of them, but enough that it becomes a problem.
I’ve seen this play out across a couple of my hobbies in the past decade. When things were hard to access, the people who put in the work to get there had an appreciation for doing it properly and being respectful of the environment and community. Once it becomes cheap enough you get a lot of weekend warriors trying to run through the process as fast as possible while seeing how many corners they can cut. Things get ugly.
Those are more likely to be reached by the DIY crowd.
[1] https://en.wikipedia.org/wiki/Atomic_force_microscopy
[2] https://en.wikipedia.org/wiki/Scanning_tunneling_microscope
I used to work for a defense contractor, with millions of dollars' worth of that kind of gear, and keeping it calibrated was an expensive pain.
For example if the magnification on the scope says 1000x but is actually 1050x, the item you manufacture and measure would have wrong dimensions that might cause issues during its use. This is why you calibrate them, so you know that something that's meant to be 1000 micrometer is actually 1000 (+ or - a certain tolerance that it's certified to). This is also needed for the certification of the products you manufacture.
However if you're just a hobbyist and want pretty pictures or you don't care too much about the accuracy, then it's not necessary.
I worked in a place with an electronics test lab and even stuff like multimeters would need to be certified yearly. This cost a lot (a significant fraction of the purchase price!) so often it would only need to be done for a few years before the meters would get replaced entirely. They'd be useless for the lab then, however they were still fully functional for home use as my need for accuracy isn't that high. Normally I use cheap chinese meters but having a real quality fluke is a big step up even if it's not calibrated officially. Unfortunately most of the stuff was scooped up by people a bit higher in the food chain than me :)
Back then (mid-1980s), even the digital stuff had a lot of analog circuitry, and some of these huge high-bandwidth spectrum analyzers (for example) would have hundreds of micro-pots. Calibrations could take days.
