Ok...then maybe she really does need to get out and take a walk once in awhile with you. I'm not a SAHM but I can imagine that they need a break from their daily routines just as I do, a mom who works away from the home. It's worth a try to break the routine somehow isn't it?
Sometimes when people are in the middle of a rut/routine it's hard to breakout....you've noticed you two are in a rut, so it now falls on your shoulders to break that routine because you recognized it. Sucks I know to feel that you are the only one who is always trying....but the way I see it, it is your responsibility to do something about the routine if you notice it's a problem.
You might just find she welcomes the change too....maybe, just maybe...she doesn't even know she needs the change.