Ian,

have you asked them why?

You have an expectation of what you want to see happen, but they may have different ideas about it. Neither are generally wrong, but its what you use that is most effective for the capabilities of the team.

Whenever I take on a new team and we touch on the ruck during some 'brainstorming', I put 2 words on the board "BOMB" or "BRIDGE" (and by bridge, I don't mean 'sealing') then spend no longer than 5 mins chatting on each, then weigh up what the team do best - or even if they equally good at both (which is a plus). I don't tell them to do either, they read the situation and make a decision as to what they think is best in the given situation.

We then go out on the paddock and look at situations where both can be used. I find this then gets players thinking of the need to ruck beyond the ball and also why they're doing it, which in todays 'thinking' game is what makes the difference between teams. The 'doing' it only gets you so far, its the 'WHY you're doing it that propels you further'.

Maybe, you might find that the practices you're using are fine, its just how you talk things through with them.