Older cars, early 80s and before, were very different from cars today. They were body on frame design.
Body on frame vehicles are very tough and stand up better to the stress and torsion off road use. And older vehicles had stiffer suspension with more travel than is typical today, and more clearance underneath. Crawl under a newer crossover like a CRV and look at how little clearance there is under the transmission/differential/oil pan. Now do the same for a 70s vehicle. Older cars are essentially trucks with a car style body. Over the years cars have evolved to specialize in highway/city driving: lower, unibody construction, softer suspension, better MPG. All makes perfect sense, much quieter and with better handling for their intended purpose. If you want to take your modern street car on roads designed for high clearance then go for it. But I recommend having a plan for getting out or spending a few days if you get stuck or crack an oil pan.
The move to unibody helped improve MPG by reducing vehicle weight. Towing capacity is not simply a function of HP, its also has to do with the suspension and weight of the vehicle. The weight of the tow vehicle is important in controlling the load and the higher the tow capacity the heavier the tow vehicle. It should be noted because it comes up often on these forms: towing capacity is not a conspiracy to sell big vehicles in the US. The reason you see smaller vehicles towing heaver loads in other countries has to do with highway laws and road design. EU and AU have much lower towing speed limits whereas in the US going that slow on a hwy/interstate would create a traffic hazard. The higher speeds in the US mean you need a more capable vehicle to keep the load under control. For everyone's sake, please don't exceed your tow capacity - unlike cracking an oil pan which only really hurts you (and the local environment I suppose) - this puts other people at risk.
Oh, and 60s and 70s Nova... MPG of around 10-15. Car body on truck frame.
Unless it's necessary for work (towing, cargo capacity, off road work sites), commuting in a truck is foolish. But they are necessary in certain situations and fine if you're only using one for these cases.