At what age do you stop putting children in shopping carts?

Similar question to the stroller at the zoo.

At what age do you stop putting children in shopping carts while grocery shopping or just out and about?

My son is 8 and I admit I still put him in the bottom of the cart and let him play on my phone when I have to take him grocery shopping with me. For me it's easier than him asking to get everything little thing, wanting to help get things off the shelf and help check out. (All those things are fine when the stores aren't busy and I'll let him help then).

I'm mostly asking because I feel like I get a lot of judgemental stares because of this.