They are made to be good enough without costing a lot (some Noctua coolers are more expensive than a whole CPU) and usually address only the lower-level enduser market, where a difference of $5 can be an important percentage of the price. But they did evolve. At least for low-power CPUs the Intel stock coolers are not noisy and work well. The AMD Wraith coolers are on par with some of the good 3rd party coolers.