Who is telling you this?
I don't own any tanks over 55 right now personally (hoping to change that), but of all the big ones I've seen at shops and friend's houses, none have had issues that weren't owner related. Such as poorly made stands that sagged or weren't square or both, being set on a floor without being leveled, large rocks not secured that fell inside after fish undermined them and cracked the glass, etc.
It's so much more important to make sure a large tank is on a great stand than it is with smaller tanks. The pressures and shear forces are much greater, as is expected.