My Maggie is like this too (she's about 2-1/2 years old and otherwise mostly well behaved). I think I've about decided that the reason Maggie does this behavior is that she thinks if she poops outside, that's the end of walk-time. My husband is especially bad about coming straight back in the house after the girls have done both No. 1 and 2. I try to stay a little longer so that they can sniff and play a bit, but still probably have cut walks a bit shorter than I should. Based on other posts here, I'm going to try extending walks/playtime past poop-time longer than it has been, and hopefully that will help.

Good luck! I know it's very frustrating to be cleaning up all that poop all the time.