Stranger, this is a fascinating question and I hope you get some responses from true ski lift technical types or professional ski biz cost benefit analysts.
You sound like you go back far enough to remember when there were a lot more surface lifts in operation in the US.
A number of us here go back to 60s, 50s or beyond and have memories of when more of these kinds of lifts were in operation. Believe a number are still sprinkled across the country, primarily serving beginner terrain. As posters above mentioned, they use them quite a bit in NZ, also Europe.
There are still some around in our region. In 2008 I rode a t-bar (with my son) at Mont Saint Anne near Quebec City. It had a vertical rise of ~1000 feet. It was such a unique experience that we rode it twice even though we weren't that interested in the terrain it served. Once together, his first time, and once alone. Pic here:
As you mentioned there is a platter pull at Beartooth depicted in the thread you mentioned here: http://www.epicski.com/forum/thread/104081/beartooth-pass-june-2011
There’s a platter pull in the high alpine at Copper Mtn. Believe there is or was one high up at Breckenridge too?
I’ve long thought that if someone had a gnarly mountainside like Silverton, CO or Mad River Glen, VT where a fair number of naturally skiable lines exist that stringing up a handful of t-bars would be a low cost/low footprint way to provide access for an advanced skiers/rider paradise. There is a group considering something like this in Alaska for a special club-like ski area project. See thread here: http://www.epicski.com/forum/thread/95909/introducing-mountain-rider-s-alliance
But here are my thoughts about why smarter folks than I have not tried this in recent decades.
Function: Seven or eight years ago I rode a steep chairlift in Austria with a guide. He said this terrain used to be served by a t-bar (there are still hundreds, maybe thousands of significant surface lifts in use in the Alps), but there were a number of bad injuries and deaths from people falling down and sliding so they were real happy when it was replaced by a chair. Think about how hard it would be to ride a surface lift up some of the gnarliest lift lines like the trams at Jackson or Snowbird, Supreme chair at Alta, tram at Cannon, NH or chairs at Castlerock/Sugarbush, VT or Mad River Glen, VT. The cliff drops would be hard to navigate or they’d have to blast them into a smooth track. I think where surface lifts are successful in steeper terrain like NZ or Beartooth is if there is a smooth ascent line up the hill without huge undulation or cliffs. Even then there is the threat of an injurious drop and roll from someone falling off the lift, perhaps sliding into the person behind them.
Cost: I’d like to see a pro lift installer talk about how much cheaper it is to install a 4000 foot long t-bar over a conventional double or triple chair? It might not be that much different, maybe a third less? And the chair would probably have much better uphill transport efficiency and be comfortable and versatile enough to handle all skill levels of riders. Some surface lift designs can be particularly awkward for snowboarders.
Glamour: lastly, great numbers of casual skier/boarder tourists who like fast, comfortable high speed quads or gondolas that climb 2000 vertical feet in ten minutes are not likely to be thrilled to travel across the country to take a cold, strenuous t-bar ride up a long, scary ascent.
I still think it would be cool for a maverick outfit to string some t-bars up a hill like Silverton and let the hardcores take it on.