It is user friendly, and it is an artistic control. Between 0.25 (1.33 water) and 0.75 (1.65 some glass types) you’re in the plausible IOR range of what a dielectric material can be, and in a fairly linear fashion which is easy to control.
Principled is a pre-set shader to make plausible normal materials, and if keeping values reasonable will not break physics - it’s NOT to create all materials you can think of. It’s second purpose is a fast audit of textures to be used within PBR metallic workflow based game engines, and for good or bad it has to match those specifications pretty closely - usually the reference specification from Disney.
What is it you’re trying to achieve? I have a suspicion relying on another node setup mixing shaders is the way to go if you’re trying to make something special. Apart from diffuse exit IOR, diffuse roughness implementation, and sheen, all other effects can be made mixing other shaders. I sometimes use Principled only to get access to these exotic features (usually sheen, which has some problems of its own).