I agree that foiling is a dead art, and rightly so. No one used foil because it was so great; we used it because foil and screens (and maybe lacing) were the only ways to protect windows back then.
Nothing would make an installer's heart sink like rolling up to a job and seeing a bunch of steel casement windows that needed foiling. Many of us wished the salesman would die a slow painful death for selling jobs like that.
Properly installed foil worked all right when new, but after the window washers beat on it a few times, problems started. Self-adhesive foil blocks dried up and fell off the window. Crossovers got ripped loose. Sometimes, the foil was on a day circuit, sometimes you didn't find out about the problem until closing time.
By the way, it isn't necessary to use foil splicing tools. The corner of a razor blade works much better. Just punch about ten holes in each side that you can see daylight through. And I've never had to solder foil in my life, and I've foiled tons of windows.
I think the deterrent value of foil today is pretty much zero. It's so rare, today's burglars probably don't even know what it is, assuming they even care. It's like expecting today's stereo thief to recognize a reel-to-reel tape deck.
If it's on your own office window, fine, but I'd never even consider supporting foil at a customer's location.