There is a difference between rolling it once and a one in a billion chance of a perfect roll… 
Also, to your point, there are plenty of items that already roll perfectly every time. Ideally you would want variance in all items. Just not the extremes currently displayed. Where is the happy medium? 1 in 1000 rolls a perfect? 1 in 100,000? Definitely shouldn’t be in the 1 in millions or billion like it is for quite a few peices with multiple variable properties…