I'm new to the forum and grew up w/ red tractors. What a great question tractorshark! You got a lot of worthwhile replies. I think we all wanted to know that. And keithnea, if you're not a big IH fan, your questions merits consideration. Speaking as an ih fan let me share my personal view & reason why many others feel the same. First consider the color red. I sell snow plows and have guys that don't want a yellow(Fisher- Western's sister or Meyer ), orange (Curtiss), white (Blizzard, Western's other sister) on the front of their pride & joy. If I was an equipment manufacturer first order of business would be red color. People are impressed w/ red. In Wisconsin most 20th century barns are red. In a crowd of women who stands out? The Lady in red. Ask singer Chris DeBurgh (Lady in Red). What color of collector cars are worth the most, esp small sports cars? Red. (Prince sang about Little Red Corvette, not Little blue or green, doesn't even sound right) Then maybe white & black comes next technical are not colors.
Next, consider some things IH did over the years. When new products came out they let everyone know. For example, Super MTA, 1206 Turbo, 656 Hydro. On the side of each of these new models up front were bold big letters telling the world about this product. In contrast, some JD tractors had the model hide back where you get on the tractor. (10 & 20 series) In addition, IH made gold demonstrators, black stripe models, the contrasting white on the new 1206, & the granddaddy of it all -- the 68 series w/ their dual chrome stacks & chrome shields. How could you not miss that. Better yet, today these models are sought after by collectors. Everyone else had turbos, hydros, V8's, but IH was market savvy in capitalizing on letting everyone know about their product.
Furthermore, my experience w/ red fans is they want tractor & equipment that's simple, easy to work on. The tractors up to the 1980's were that. Many of you guys do you own major engine work, TA replacement, trans & rearend repairs. Or you have friends that do it. Recently I ran across a thread from a guy asking if he should stick several $1000's in a 706 for repairs. Overwhelming it was fix vs trade. I can't imagine anyone doing that to a nearly 40 year old tractor unless it was worth it. I grew up in the 60's & 70's and we had a few of ever manufacturer in the neighborhood. Today the red are about all that are left esp from the 1950's. Even JD from that era are not used much. I'm not saying they or others aren't being collected by enthusiasts, but what a testament to reliability when 60 year old tractors are still being used. Probably the biggest reason many aren't used more is they are not big enough (esp the trend here away from dairy to cash crops) and lack of options( LPTO, no 3 pt, ps, cabs, etc). Moreover, when you work on your own equipment, there becomes an attachment that isn't easily broken.
Here's my take on part of the downfall of IH. Farming in the 60's & 70's was changing rapidly. Few farms, farmers, bigger tractors, equipment, etc. The number of dealers, and pieces of equipment was getting less. Add in the fact many parts of the country were practicing reduced & no tillage, Haylage replaced baling, Combining grain corn replaced picking. (The farmer renting my land does one past tillage in the spring- & does a better job then we did 40 years ago w/ multiple passes.) Everything is done faster w/ less labor. So tractors & equipment probably lasts longer. All the major tractor manufacturers were in trouble except JD. A tribute to them and the quality of their product. Will IH ever be back on top? I doubt it. It seems there are more short line manufacturers then ever- building quality tillage, planting or harvesting equipment. The competition is too great.
So why is IH so popular? Maybe part of it is unjustified, but they built a lot of quality equipment that made farming easier. However, much of it has to do with the many comments found in this forum. I've found that no matter what you like in cars trucks, snow plows or tractors, some people will love a brand the next guy will curse. Much of it is perception. What a great forum. Thanks for letting me speak.