A couple of guesses are that they are more traditionally associated with the product (nylon started to be used in 1994 on SAKs I think), the metal swiss cross on the celludor looks nicer than the painted silver on the nylon (probably has to be done this way for production reasons), and most folks equate economy with lower quality (years of training in a consumer culture). I personally prefer the matte handles but that's just me.
There are 84mm and 91mm versions of several victorinox models. More have been appearing in my area lately (just in the past few months), so they appear to be catching on around here. I haven't seen them on any websites either. The "thinner blade and tools" discussion was actually two of us unknowingly comparing different models (84mm vs 91mm). The 84mm doesn't pause at 90 degrees, but the 91mm does- just like their celludor counterparts.
The only time I have run across one of the economy models was at Lowe's. They had a few Recruit IIs packaged with Mini Mag AAA lights on clearence. I really like the nylon scales, myself. You can carry them around in a pocket full of change and keys and they still look new. They don't show scratches like Cellidor does.
Back in October and November of 2005, Walgreen's stores were having a clearance sale on their Victorinox Classic SD and Sportsman II SAKs. The Classic SDs consisted of the red cellidor models, along with translucent-handled versions. The Sportsman IIs had the matte red nylon handles of the "Ecoline" model. You might still be able to find a Walgreens that has Victorinox SAKs on-sale, as they apparently didn't sell too many in a "drug store." One other "difference" between an Ecoline and a regular SAK, is that the Ecoline models don't have the detent at the 90-degree angle, which can come in handy.
Here's the link to the thread about Walgreens SAKs on sale.