I won't speak for everyone, but for me? It doesn't just increase a number on my character sheet. It does something that is very hard to do otherwise. If you have one of these items, there is a very good reason--and probably a very good story--behind it.
"Today, we descend into the heart of Burning Mountain to face the great dragon known as Moltenwing. These necklaces will allow us to breathe the suffocating, oxygen-less atmosphere within the lair of the beast!" *cheers*
"Today, we descend into the heart of Burning Mountain to face the great dragon known as Moltenwing. This rock will increase our Proficiency bonus by one point." *sad trombone*