[elpatoisthebest]

The problem with Robinson helicopters specifically (older R-22 & R-44 more than most) is their very low mass rotor system, which results in very low inertia. The time you have to recover is significantly shorter than other high inertia systems on other helicopters.

Their very low cost makes them pretty common for schools and instruction in general, but the low inertia (and resultant fatalities early in its operation) was significant enough that the FAA requires a Robinson specific endorsement.