I drove an SUV in the ‘70s, my ‘73 Bronco Ranger. I had friends with CJs, Blazers, Scout, Jeepster, they were popular as were pickup trucks, just not as popular as we also had wagons (LARGE wagons).
Cars were larger, we could haul a lot in a car.
As the fuel embargo hit us and fuel prices escalated in the late ‘70s and into the early ‘80s, people looked for smaller more fuel efficient cars, CAFE forced the automakers to make them so that we could buy cars built on-shore.
Hatchbacks became more popular, blended the utility of a wagon with the size of a sedan, which helped us to still haul things in our cars, but it didn’t replace the wagon/estate. Some of us still bought wagons but it was a small segment and the resale on them was not good.
As fuel became “cheap” again in the US, pickup trucks flooded the market. Money was cheap also so pickup trucks became luxury vehicles. SUVs surged as the soccer-mom vehicle in the pickup truck family, fuel efficiency was not important, and large SUVs replaced the large sedans of the ‘70s and ‘80s as the vehicle of the affluent, put chrome vents and undercabinet lights on the outside of a Tahoe and you now have an Escalade, … everyone was doing it.
I lived in a region where 4WD and AWD was important, I drove quattros and 4Matics in the ‘80s and ‘90s, and back to SUVs after that. I hope that my 2016 (purchased new) diesel full-sized AWD SUV stays reliable for many more years as they have discontinued exporting the diesel/bluetec to the US after 2016, and I love the 30+ MPG city and 35-40mpg highway (depending on speed) that it delivers, hauled out our 24’ boat with it yesterday with enough torque to walk up the ramp just above an idle. Large, quiet, safe, smooth, and fuel-efficient with less greenhouse-gas than a gasoline vehicle I just love modern turbodiesels. Large SUVs don’t have to get bad mileage, but we are used to putting up with it so that we can have 400hp gasoline engines and aerodynamics of a brick in most offerings from Asia and the US, … I digress. My new/gasoline version of the same car is of course faster, but loses almost 10mpg and doesn’t have the towing grunt.
So why are SUVs (and large pickup trucks) so popular? Fashionable, practical, safety, comfort, all of the reasons listed in this thread so far plus the simple fact that they’re available and affordable to the masses. The manufacturers will continue to make them as long as they are selling, especially the profitable premium models.