Put some of these cheapo scopes on a rifle that has some recoil, say a .300 Weatherby, and before you shoot 100 rounds it will come apart inside. Usually when you zoom the power from low to high, a shift in bullet impact will result, adjustments will not be accurate or jump all over the target, etc.
I have to agree with Graybeard, Good shooting= Good rifle, good ammo, good optics.