I agree with Dag.
The cars of the late '50s through the late '60s were–in most cases–long and low just for the sake of being long and low. Just as clothing fashion is not necessarily functional, car design in those days was rarely functional.
In order to make people want to buy new cars, it was necessary to make their old, relatively high, cars look dated. That, despite the reality that the somewhat higher car made much more sense in terms of passenger accomodation and comfort.
As Dag says, the seats tended to be very low and uncomfortable. That made getting in and out quite a pain–literally for older people. The “dogleg” roof pillar necessitated by some of the new “wrap-around” windshields was just dandy for smacking your kneecap while entering or exiting the car. The middle seat was indeed very uncomfortable, simply because the extreme lowness of the cars made for a very large transmission/driveshaft hump in the floor. The legroom in front was often severely hampered by the intruding trans hump, and the middle seats were a mere thin bit of padding over the intruding driveshaft hump.
The rear trunklid and overhang (sometimes almost as large as a ping-pong table) provided a HUGE trunk. Unfortunately, the extremely weak rear springs on many cars made it impossible to fully load the trunk without the rear suspension hitting its stops on bumps. And, the extreme rearward pitch of a heavily-loaded '60s era luxo-barge also meant that the headlights were mostly illuminating the trees, rather than the roadway.
The exception to the rule was Studebaker. Their cars, which were only cosmetically changed from the early '50s, were just as roomy inside as the huge land yachts of The Big Three, and lacked only the extreme chrome decoration, huge overhangs and excess exterior dimensions of the cars from The Big Three. Studes were also more economical and had good acceleration and handling as a result of not being oversized behemoths. The US public rewarded Studebaker’s clean, simple designs by avoiding Studebaker showrooms to a large extent. The rest is history, sadly.
As a bit of nostalgia, it is nice to look at the cars of the '50s & '60s. However, in a practical sense, I suspect that few people would really want to return to the wallowing, essentially unsafe by modern standards, uncomfortable, maintenance-intensive gas hogs of yesteryear.