I think there is a difference between stackers and collectors, when it come to grading coins.
In most cases it makes no sense to stackers to have there coins graded, as the buy them for the metal content not the collectors value of the coin itself. And most of there coins are made for this purpose, that's why the come it tubes and not in a fancy box.
For collectors it's different, but it also depends on what you collect. I mainly collect pre 1935 Dutch coins in mintstate condition, where MS64 is the lowest grade I want. I do grade all these coins with PCGS (sorry Numi) If I buy them