My guess is that Victorinox cut the 74mm line to push the 58mm line. I even think they'd cut the 84mm line if it weren't for the fact that the small selection of Waiter, Bantam and Recruit are still top sellers so they just can't do it.
My guess is that Victorinox knows very well that city folks will likely do fine with a 58mm SAK. And the adventurous folks doing camping and long trail hiking etc, have more need for a full scout pattern type of knife like the 91mm SAK.
In my opinion it's a sad thing that they cut the 74mm line and decimated the 84mm line, but I think I can sort of understand it. The 65mm line with basically only a single model, is likely kept alive as an gesture and historical nod to Wenger.
I think you just may have hit the nail on the head.
I don't think Victorinox has been in business since 1890 by being dumb and trusting to luck in making decisions. They have great business sense, and a great production capacity. I would not be surprised at all if they did an exhaustive market study, and came up with a streamlined plan for sales in the greatest centers of populations; the cities. In this 21st century, the mass of the human population is not with farmers, trappers, frontiersmen, ranchers, and others in the boonies. It's in Tokyo, London, New York, Paris, Chicago, Frankfurt, St. Louis, Rome, and the like. The teaming masses of people now live in huge urban settings, and those urban settings have limited us of a knife, but have many laws about them. From Amsterdam to Tokyo, there's laws governing what kind of knife can be carried.
I have a moderate size hunch, that the 58mm line was carefully selected for the ubiquitous "world acceptable" pocket knife/mini multitool. And it has been successful. Victorinox is still the worlds biggest knife producer, with world wide distribution than makes others look like small time pikers. I doubt Buck, Benchmade and Spydeco combined, could match the production numbers of SAK's shipped out per year from Switzerland. And a great deal of that production is the humble little 58mm's. I can't begin to make a guess how many classic's, ramblers, mangers, are shipped out across Europe, Scandinavia, North America, South America, Japan, Southeast Asia, and mideast. Sales in just the U.S. is in the millions, as you can't walk through any big box store or sporting goods store here in the U.S. without seeing the classic in many colors having from a peg for the price of a fast food lunch. Heck, they give them away with advertising and company logo's on them. I've got a few with advertising from a finance company, a company selling oil drilling equipment, and a medical equipment company. I understand in some places, you can now carry them again onto an airliner.
In today's world with dense populations, it's a cutthroat market in many things. Look at the car brands that didn't make it this last big meltdown. No more Pontiacs, Oldsmobiles, Mercury's, and others. Even huge Toyota cut their line by dropping the Scion line and streamlined production. Knife companies have done the same. They have to appeal to the most broad customer base they can, and that's the non knife nut, or non car nut, or whatever. Like why the humble Toyota Corolla or Kia Forte or Honda Civic sell like hotcakes, but sales of Jaguars, Porsche's and Ferrari's are way way less. Just like the non car nut guy will just buy something reliable to get to and from work, the non knife nut will just by something small enough to be almost unnoticed in a keyring, low cost enough that is an easy buy, but enough to do what needs to be done most the time, like opening mail, plastic packaging, and an occasional piece of twine.
The classic is the penknife for the 21st century.