I am an academic geologist and part of what we do is go around and, to put it in the worst light possible, destroy rock formations.
Students are taught to be very careful - in most cases all you need is just a small fresh piece (not surface-weathered), and with practice you can obtain that without leaving obvious evidence that someone swung a rock hammer at the outcrop.
In state and national parks and other protected areas, the rock hammers get left in the car. But I’m spelling this out for a reason - even in parks, most rock formations are nothing special and are of very little scientific, aesthetic, or other value. The rock hammers get left in the van when geology students go to parks, but there’s really no reason not to pick up and break apart rocks that have already broken off a cliff face (or whatever the case may be).
The problem is, laypeople (and even most geology students) are not in a position to know what’s valuable and what isn’t (and I don’t mean economically valuable - if you strike gold the value is obvious, and whatever scientific or other value it has is doomed in that case).
For example, when you see stuff like this - all the precarious formations of all kinds all across Utah - it is impossible to wrap your mind around the timescale involved. Each and every formation has been there for tens or hundreds of millions of years, and the original orientation and position of the rock is what’s valuable scientifically, not the rock itself. A unique landscape like that is a PhD candidate interested in certain aspects of sedimentary geology’s dream, and each “goblin” is statistically valuable to that research. And never mind the fact that it’s guaranteed to have been studied extensively already - there are always new techniques etc. and other reasons to go over old ground.
Another example is in Death Valley. Outside of the dry lakebed areas, the rocks strewn about have been sitting there undisturbed by weather or animal for hundreds of thousands of years (if not longer, I can’t remember) - a fairly unique circumstance. They develop a reddish black patina called “desert varnish”, which can be accurately dated, which is very useful - only on the side facing up, and the orientation can be important, so disturbing the rock in any way destroys its value. Most people who visit don’t know that, and even if they were told, they wouldn’t understand why it matters. Because even the park rangers aren’t experts in everything, a blanket policy of preventing all forms of destruction (no matter how small) is absolutely essential.
And of course, there is plenty of scientifically important stuff not protected by parks - it’s not always obvious. All across the Appalachian Mountains are tiny geologic clues - because those mountains are old, eroded, and tree-covered, it’s much more difficult to find outcrops that tell you anything than out west. Entire theories and important facets of knowledge are based on single outcrops, and even single tiny rocks.
One example I know of is pretty interesting. Ooids are small spherical concretions within sedimentary rocks; calcium carbonate or similar minerals that formed around a grain of sand or other nucleus under the right conditions. You can sometimes see them with the naked eye, but usually a hand lens is required. They’re fairly rare. In the Appalachians, which have undergone a lot of tectonic stress (faulting and folding), you can find oolite (rock formed of ooids) that has been tectonically deformed - the spheres are squished and elongated. Measuring the deformation gives you an incredible wealth of information about the tectonic forces at work that can be obtained in very few other ways.
There’s a known outcrop that contains deformed ooite that I went to on a field trip as an undergrad student. The professor had been there every other year or so for at least twenty years, and said that because some people take samples from the outcrop (since it’s rare), it’s now almost impossible to find something to see. The ten or fifteen of us spent half an hour searching around, and we did eventually find a piece to look at - but not before a large boulder (kill-by-crushing size) was almost dropped on some students by people who climbed up the cliff to try to find this thing (it was me and another guy, not going to lie).
So in a weird way, there’s actually some truth to these guys’ assertion But if it hadn’t been for people destroying the outcrop in the first place, we wouldn’t have been driven to climb up where there were loose boulders.