"Will someone please tell me the advantage (if any) of triggers and hammers with holes in them? Seriously. And please don't say "weight reduction", okay."
Okay.

Here's the three-hole trigger explanation:
Xavier Thoughts: 1911 Trigger Changes
1911 Trigger Changes
I was asked recently why custom 1911s almost always have a skeletonized silver trigger. It is a fair question. After all, if the 1911 is supposed to have such a wonderful trigger, if that is the allure of the gun, then why do people always swap it out?
GI triggerOne of the beautiful things about Browning's brainchild is the single action trigger can be tuned to extremely light pull weights and extremely short strokes. In bullseye shooting, it is not uncommon for pistols to have triggers so light that hummingbirds hovering nearby can set them off (not really, but almost). Trigger pulls this light are desirable in bullseye to achieve extremely precise marksmanship.
A problem arose with the 1911 however. Under recoil, the heavy machined steel trigger would bounce, causing the pistol to shoot doubles, and sometimes triples at very light trigger weights. The wider trigger shoes often affixed to 1911 triggers in those days only exacerbated the problem. The first solution was to drill holes in the steel trigger shoe to lighten it up. A lighter trigger would not be so subject to bouncing under recoil. In those days, aftermarket parts were not available, and gunsmiths fabricated parts rather than swapping them out.
Vickers triggerSoon, three round holes in your trigger became the sign of a top flight trigger job. Then aluminum triggers came on the market. Of course, the new fangled lightweight aluminum triggers had the same three holes, so everyone would know you had a trigger job on your pistol. These triggers have a set screw in them for overtravel adjustment, but they have no provision for pre-travel. If I remember correctly, Videcki was the first out the chute with this lightweight "pow button", and Bill Wilson was quick to catch up. This type of trigger is today frequently seen in off the shelf pistols.
McCormick triggerOther, even lighter triggers soon appeared on the market. One of my old favorites, the Dlask trigger, has a magnesium shoe and titanium stirrup. It can be adjusted for pre-travel as well as over-travel. The Dlask trigger was my favorite for a long time, simply because of that adjustment capability. Then, Chip McCormick introduced his lightweight trigger which caused a sensation. It was a less expensive trigger than the Dlask, but allows the same adjustments. There are other triggers available with changeable shoe lengths, plastic shoes, and even shoes with ball bearings. None of these special triggers constitutes a trigger job by itself. A 1911 trigger job occurs on the sear and hammer hooks, not in the trigger guard. Like chrome valve covers on a hot rod engine, these aftermarket triggers are just visible indicators that a trigger job has been performed on the gun.
Solid aluminum triggerToday, most off the shelf 1911s have skeletonized aluminum triggers. These are usually of the three hole "Videcki" design, making the triangular holed McCormick trigger the sign of the custom trigger job. Ironically, many top flight pistolsmiths are moving back to the solid aluminum trigger today. The skeletonized aluminum triggers were and are all about fashion. The skeletonization is simply not needed in an aluminum trigger. Thus, the 1911 trigger has come almost full circle in outward appearance. What is old is new again.