When going out, every time I let my daughter sitting on the trolley first. So, she is very happy and knows that she can go out.
My daughter likes walking very much and sometimes refuses to sit on the trolley even she is very tired. Then I will give her some juice or biscult and ask her to sit. So, she can take a rest and I can have a break too. If we go out before her noon-time sleep (seldomly), she can also sleep on the trolley. And, if my daughter doesn't sit on the trolley, then it can be a "luggage car".
Once we practise not to bring the trolley, we cannot use the trolley forever because our baby will not be willing to sit anymore. At this stage, our babies of course are very willing to walk. However, after maybe half or one year, they will always ask us to hold them and are not willing to walk. At that time, it's too tired for us!