Is ground noise really normal? If so, why?

A certain amount of noise is indeed completely normal. What is a completely normal amount of noise for vinyl is also a lot more than the near dead silent white noise you and your kids are used to from digital. (That the digital signal is itself noise is a whole other story.) Exactly what amount of noise is completely normal however is hard to convey sight unseen in a forum post.

What I do know for sure however, there is no ground noise. There is groove noise. Surface noise. Ground loop hum. Radio frequency noise of all kinds and levels. Seismic vibrations of all kinds. Ground itself however is where spare electrons go to die. Ground is ground. To have good ground is almost by definition to have no noise. Ground itself is the opposite of noise. It is the anti-noise.

So what are you talking about? Hum? How much? Sounds like its only audible in the silence between tracks??

Well white noise is a thing. Like pink noise only with more treble. Dead silent is a thing, its the complete absence of noise. Near is a thing. It means close but not quite there. So yeah I would say near dead silent white noise is a thing.

Sadly, hum is quite often the norm. It does not have to be! A properly set up system can be dead quiet, where all you hear is groove noise between songs.

Hum is a system-level issue, not due to any single component (unless it’s a crappy  design). Here is some more info:

http://www.hagtech.com/pdf/eliminatingnoise.pdf