A bit like Gallaxhar trying to give orders his clones in MONSTERS VS ALIENS, I'd guess (tried to find the clip, but failed).
While true, I was joking a bit too, since Archie doesn't use The Shield character a lot, Marvel's is safe from additional legal action as the suit isn't an active trademark (plus they redesigned the Shield's outfit to be less shield-y so it stopped having the distinctive look) so have used that shield for stories set in the period Cap carried it in the comics.
EDIT: I looked it up, MLJ didn't sue, they asked Martin Goodman (who the MLJ founder, Louis Silberkleit, was friends with and I believe all three had worked with Goodman at an early point in their publishing career) to change the shield since they got there first. That's why the one shield only existed for the first issue and was changed to round for issue 2. As mentioned they subsequently went back after the trademark issue wasn't an issue and did re-introduce the original shield as historically happening in Cap's timeline.