I clearly said "in practical terms," LOL!
And you've been given some practical information, no?
Here's a little more:
To clarify: The dB is the decibel. The numbers are on a logarithmic scale such that a 10dB change is perceived as being twice as loud or half as loud (I'm sure Cuda meant this, not the 100 times difference typo he made).
So, a difference of 8dB reduction is REALLY significant (perceived by our ears as almost twice the noise let-through), especially when you factor in the loss of isolation caused by glasses, as arizona98tj pointed out.
When you consider that the impulse SPL of most pistols and rifles are in the 150-165 dB-SPL range, and permanent instantaneous hearing damage can occur at 125-130 dB, you will want all the protection you can get. Don't forget that multiple shots fired at the same time do increase the total impulse, but more like +3-6 dB each, not a simple doubling.
I value what's left of my hearing, and I use both the foam plugs and -30 dB earmuffs. It is somewhat inconvenient to communicate, but I can still do that by just pulling my muffs back on my neck.
I realize many people have served during wartime when hearing protection was not available, but ask them how hard tinnitus sucks.