Not a true expert, but I think it comes down to "observing" a particle/phenomenon like this inherently comes down to some sort of interaction, and it can't just be neglected like you could on a macro scale. Even for something like holding a ruler up to an object and seeing what mark lines up, you're relying on a bunch of light bouncing off the object (and the ruler) to be able to judge that. If the thing you're trying to measure is on the order of one particle of light, blasting it with a bunch of anything is gonna affect it pretty severely, and who knows what a "ruler" would even mean in that analogy. So it's less like some idea of sapient knowledge, and more like when you struggle to measure something like a tiny feather or single bead of Styrofoam, like you can't even get near the thing without the wind from moving or some random static or something else moving the thing around uncontrollably, except many orders of magnitude more sensitive.

Question for the ages