Why Don't Devices Have Built-In Ground-Loop Isolation?

[nintendoeats]

I now have the joy of having installed two ground loop isolators in my computer's audio setup. Given that 99% of people probably have no idea what that is, I'm wondering why these things don't come built in to equipment at the mid-range and up. I'm sure that many a person has dismissed Brand X as "sounding like crap" because of ground loop hum, so it would behoove manufacturers to include internal mitigation. Is there some horrid disadvantage of which I am unaware?

 

[amirm]

It is not a common problem so it is not always addressed. I agree for anything pricey, it better come with one.

 

[nintendoeats]

It is not a common problem so it is not always addressed. I agree for anything pricey, it better come with one.

Guess my equipment isn't posh enough

How widespread a problem are ground loops, and why does it affect some setups and not others? I basically assumed it was a normal thing since it's something I've been dealing with in my PC system for years.