To put that in somewhat more technical terms:
"Kneel" is an active verb, a command. It is not a continuous verb that describes a constant state of being. Therefore, the "kneel that location" text cannot be a continuous effect. It has to be triggered or passive.
Well, triggered or passive effects need some sort of timing information to let you know when they initiate. "Kneel that location" tells you nothing about when that text should initiate, so while it must initiate when it first becomes active (i.e., when the attachment is first played), there is nothing telling you to initiate the effect again (and again, and again) each time the location stands.
So, long story short, it's an active/command verb without any play restrictions telling you when it will be initiated. As such, it cannot reassert itself just because the location is standing.
And, just for fun, to put it in practical terms:
Let's say "Kneel that location" is a continuous effect that reasserts itself every time the location stands. That means any "kneel that card" effect without a duration should also reassert itself every time the card stands, right? So, since something like You Killed the Wrong Dwarf (Any Phase: Choose and kneel a non-NOBLE character) doesn't say "until the end of the phase" or "until the next standing phase," the event should continually reassert itself for the rest of the game. Since this is clearly not the case, the "kneel that location" text should not be able to reassert itself, either.