I don't get that either.
On a bad day I file maybe 10 times, most days when the ground is frozen I'll have to touch up the edge twice.
On my 18" chain a touchup takes 2 minutes at most on the 24" a little longer.
Of course, the chain is severely rocked and case hardened by the snow, it is another story, but how often does that happen to a pro?
Twice or 3 times a week in peak season, maybe.
Since most poeople don't run their saws 2000 hrs a year like I do, I think the time saved by switching to semi or full skip is negligible.
BTW, regarding sharpening.
When I get a new apprentice, I show them a calculation of the price of an 18" chain ( imported from the US, or it won't work) and an hourly wage for a timberfaller ( not that we get paid by the hour, I'll die before I'll be falling at a fixed houly rate!)
That calculation shows that if they spend more than 15 minutes on sharpening, it is cheaper to toss the chain and mount a fresh one.
Then I procede to my how to freshen up an 18" chain in 30 seconds showoff.
One stroke per cutter and the saw set up in a Scandinavian filing stand, and that is all it takes.
Combined with the message they get when they start, that we won't tolerate a saw that doesn't cut optimally being run, means that a couple of months into their first logging season, they can and do sharpen like pros!