Why do we bother with faucet aerators (which simply get clogged)?

My faucets were almost totally clogged with hard water deposits (I'll call
that whitish greenish coating lime for lack of a better term).

So, at Safeway, I picked up LimeAway and put the satin-finish faucet tip in
a cup of that over night.

Unfortunately some of the faucet metal was etched away to pink copper (what
is in LimeAway anyway?) but the good news is that the holes unclogged in
the aerator screens.

Now, I can tell from the name that the aerator puts air bubbles in the
water at faucet, and I can see a difference with and without the aerator
.... but I don't really see why it matters.

Please edify me.

What's in limeaway anyway (that etched away the satin coating)?
Why do we bother with aerators anyway (which simply get clogged)?