No one ever said that double adjustable shocks weren't absolutely any better than non-adjustables. This is clear. But the marginal improvement relative to the money spent is minimal compared to the other things you can spend money on. The 1000 bucks spent on top notch shocks can also get stall and gears, which for a street car is so much more important. Or it could get a cam swap, or T bars and a sway bar, or leaf springs and subframe connectors, and the list goes on.
It all boils down to the economic principle of cost minimization. Your money is best spent where the improvement to the car in proportion to the money spent on each upgrade is the same for every upgrade.
So for a low budget street car, save the dough and put it towards good heads or something. On a nice car, by all means...