Most people don't put as much thought into a vehicle purchase as you are.
This is accurate.
Where we live diesels require emissions testing every two years.
Same here (Jefferson County). It's been a while since I had a diesel, but IIRC, it's opacity and super easy to pass.
I think you’re seeing so many Tacos because for the longest time, the Taco was basically the only mid-sized truck on the market. Sure there was the Colorado/Canyon but until the recent gen, I’ve hardly seen them in traffic. I could speculate as to why, but it would just be speculation. There was the Nissan Frontier, but if you’re going to buy a brand new truck with 10 year old technology and styling, might as well buy a Taco to get that perceived quality that everyone likes to talk about. When the Ranger was in production prior to 2011, it was the king of the US midsize market- for its entire run. Will the Ranger regain its place at the top with the new release? Hard to say but it should give the Taco a good run and Toyota better up their game and bring the styling into at least the early 21st century.
I was only counting current models. There are definitely more older Tacomas because they practically were the market for years. If I'm only looking at brand new (or indistinguishable from brand new) trucks, that's where the observations are based.
Automotive Sales Data and Statistics
www.goodcarbadcar.net
Your point about the old Ranger being at the top brings up a point, though I'm not sure your numbers are accurate. Going back pre-discontinuation, the Ranger was discontinued in 2012. Going back to 2005 (arbitrary year just back enough for some numbers), the Tacoma essentially doubled Ranger sales every year until it was discontinued. The Ford F-Series is, the best selling truck in the US. That only makes sense once you realize they're counting all f150/250/350/etc. under the same column. Looking at the same dataset, GM had 9 different truck models sold in 2005, all were accounted for separately, and totaled up trounce the F-Series. It sorta goes back to the following...
I see you're in Colorado and that might explain the difference but I see them here in SE TN all the time. They seem to be favored among mudding farm boys who couldn't afford a full size chevy. Nothing remotely "overland" or "expedition" like - all muddy beat up old colorados with baja bars. It's a shame really. Keeps me from looking at them for the same reason Dalko above doesn't want to be associated with the toyota bro crowd. Even though the new z71 long bed has something like 1800 lbs of payload in a crew cab configuration which outdoes the ranger significantly.
What the majority of people do may, or may not, have any bearing on the quality of the thing. Chili's comes to mind here. Similarly, the quality of those people may, or may not, have any bearing on the quality of the thing. BMW comes to mind here. I avoided buying a BMW for years because of the distinct ****************** vibe. Then when I needed something cheap and fun, but new enough to have safety features after my accident I'm glad I found a good BMW. That extends to the stereotype of mid-size Chevy trucks as fleet vehicles. Pretty stripped down, and thoroughly abused. Obviously, that's more about fleet trucks than Colorados, but they're sort of one and the same from a reputation perspective. That said, I intend to get my truck in white so that I have maximum availability of pre-paint matched parts from all the fleet trucks (and because no non-metallic capital-C Colors are available for similarly practical reasons).
One of the things I liked most about air cooled VWs was that they were classless. In my club, we had truck drivers, engineers, a surgeon, and I guess I was an business executive at the time. People will have their ideas and opinions of what kind of people drive what kind of car, and to some extent those stereotypes can hold water. Mayhap one way to establish character is to break the mold of the stereotype for the platform... For instance, a Porsche with a lift and knobby tires is an immediate character bomb by the very act of its existence. If a truck is firmly established as a redneck beater or an unloved fleet tool, then shows up as a serious off road ************... It's not at all in the same class, but definitely in the same direction.
Then there's the element of specific individual and application. If VW were to come out with a truly viable and faithful revamp of the 50s/60s bus, I'd have a hard time not putting one in my garage, because I have a history with and affinity for buses. There will obviously be a hard minivan stigma, but all bus pilots know a bus isn't a van, it's a bus. If you want to get really technical, it's a station wagon. If I didn't want load/cab separation, I'd probably be looking at vans before I'd get too serious about an SUV.