Likely, that is the reason. But here's the thing...they've probably been there so long that if they aren't asking now, they aren't going to. And you can coach until you're blue in the face, but if they won't ask, they won't ask.
And it's possible that the person you went through was just on back up from the sales floor. And they will ask even less than the cashiers...and there's not a whole lot you can do about that.
Also, keep in mind, if this is a high volume store, there may already be one GSTL. So you will need to work with them and won't be able to come charging in and stomp on their toes. Even if there isn't another GSTL, coming in and immediately coaching everyone for not asking will not win you any friends....nor will it get you more REDcards...because then they'll ask...but without their buy in, their asking will be just enough to get by and noting more.