I ended up getting a double stroller out of desperation after DD was born. I found myself in a scenario of chasing DS down (who was 20 months) while carrying DD who did not want to be worn and needing a place to put all of our stuff, a single stroller just wasn't cutting it. We went to a spray ground a lot that summer while I was solo and DD was a tiny infant, so it gave me a place to set her down so that I could interact with DS without her getting hurt while being worn, and it gave me a place to put snacks/diaper bag/etc. and a place to confine DS too when we needed to get out of a place in a hurry and he was less than eager about it. Even now at 1 and 3 we still use it when we go to the mall because it gives me a place to stash bags and keeps everyone happy because DD isn't so pleased with babywearing anymore. I never used it for grocery shopping because it's easier to put one in the cart and wear the other, but for outings when I needed a place to put DD down it was great.
It would obviously depend on how well the child does with walking independently but it ended up being a great purchase for us since DS was/is a sprinter and I was having to juggle them on my own so much of the time. It made getting out of the house less daunting for sure.
Also wanted to add that I have a double jogging stroller as well that was a gift, and it's great when we're doing outdoor activities or walking/jogging. It's way too big to use indoors, though.