Upping any attribute/tendency slider that high would negate the differences between the players individual rating.
For example, let take your example, on ball to 100. So OBsteal that high would produce a 50 point slider increase (50) being default (so no rating change @ 50) that 50 point increase in turn would increase all player ON steal tends. by roughly 75 points, with a 99 max cap. So basically all players would now have a 99 OBsteal tend and not every player should have a 99 in that rating/tend, right?
That would be the main reason why I don't max out sliders, basically to me it negates the individuals ratings and if we are going to do that then what is the point in rating players differently if we are just going to 'slider' them to all be the same.