For me it was the ability to carry passengers. I had a Tacoma extended cab that I liked but there always seemed to be an occasion for me to carry at least 2 other people and it became such a PITA that I sold it for a '99 4runner. The 4runner turned out to be a much better vehicle for what I needed. About the only thing I would ever need an open bed for would be to haul a motorcycle but I have a flatbed trailer that is easier to load than a pickup anyway.
Since then I've had another 4runner (an '07) and now my '04 'Burb. I didn't even consider a pickup as the Suburban is more suited for my needs.
Actually, I guess that's not 100% correct: If I'd been able to find a decent Avalanche in the same price range I would have gotten it but Avalanches are not that easy to find, always have high mileage and the prices are much, much higher than an equivalent Suburban or Yukon XL.
The nice thing about having everything under one cabin roof is that you can actually carry very long or bulky materials, in some cases, the usable space is bigger on an SUV than on a pickup. Think about it: a crew-cab pickup with a short bed can carry at most, cargo that is 5'8" long or maybe 7' with the tailgate down (and of course, if the tailgate is down, whatever you're hauling is now exposed to the weather even if you have a topper or shell.) OTOH when I remove the 3rd row seat from my Suburban and fold the 2nd row down, I have over 8' of space and it's all covered and secured. The only pickup that ever had this capability was the Avalanche with its disappearing midgate.
Another thing I've noticed in years of car shopping is that when you look at a pickup and an SUV of similar age and mileage, the pickup is almost always more beaten and used, while the SUV was often a "soccer mom car" that is still in pretty good shape. And to top it off, the SUV is usually less expensive!