That is why I hate focus groups (or wherever that data is coming from).
Of course it's going to be more popular to press a button and then get instantly rewarded, preferably with an Achievement pop up on top; and ideally every 5 minutes or so so the player keeps sitting in a constant stream of "you did this thing! Now feel good about it!"
It's the equivalent of wondering whether chocolate is more popular than a carrot. Yeah, obviously.
But it becomes a problem because the player becomes conditioned towards it. Then what starts out as a small bonus on top, as seen in EU, is one day the only thing worthwhile doing. Why bother with complex mechanics? There's no clicky-make-me-feel-good button so the player doesn't care anymore; they've been taught not to care (and even worse if you can't get an achievement for it; why would anyone bother with anything if there's some vague virtual pat on your back at the end of it?!).
Eh, maybe I'm in too negative a mood, but this feel very much like a self-created gaming hell that we're now stuck with ^^