A LOT of it depends on engine size, smaller engines cannot give away power due to lower rpm, power that bigger engines still have due to being bigger. At those lower engine speeds TORQUE is what moves the car, the smaller engines have none and so they spin higher to try to pull up horsepower instead as a replacement for torque. Torque is always the better way to do things though.
Even all the V-8s I ever drove also spun higher than 2000, more like the 2500 or so mentioned. 2000 is lugging practically any engine at higher loads than lower gears add, they wear out faster that low in speed. Spinning faster past a certain low speed lowers individual hits from pistons that left alone turns into battering damage on bearings and other parts. No engine is balanced perfectly and that shows up more at slower speeds too.
I HAVE commented before on how fast the 5 speed spins the motor in top gear, it seems they could have lowered it a bit for more mileage.