It is only that easy if you put on those ugly lab coats.
Here is the reality of it:
Making low-level measurements is a PITA. A few years ago I was plagued by ~60 kHz switching noise from fluorescent lab lights (the modern little power circuits for them run at that frequency). The SMPS in our boards run up around 500 kHz so that wasn't the problem... And 'scopes, including the slew of $500k models in our test lab, are very susceptible to common-mode noise from the chassis ground. (Note a 'scope, especially a DSO, is generally not a good tool for low-noise measurements.) For low-noise measurements you need to play all sorts of games, from using good (100% foil shield, not braid, or just braid shield) cables, careful grounding (preferably star), excellent shielding (spent a good part of my career in a screen room), DC lighting, etc. etc. etc. In a previous job the screen room was very well isolated to include specially filtered incoming AC mains, DC lights powered by 12 V batteries (chargers off during measurements), and multi-layer screening with additional mu-metal shielding. That small room cost more than many houses. And we still often used small screen boxes for sensitive tests. A screen room does no good if the test equipment is the main noise source...
To put into context:
0 dB = 1 V (for reference)
-60 dB = 1 mV
-80 dB = 100 uV
-100 dB = 10 uV
-120 dB = 1 uV
-140 dB = 100 nV
-160 dB = 10 nV
It does not take much to corrupt even a -120 dB noise floor! I have (rarely) made measurements into the fV range (but would not willingly do it again). I used a leaf electrometer, but an even cooler (no pun intended) version uses a SQUID (superconducting quantum interference device).