This has always perplexed me too. I deliberately buy clothing that hides stains well. Our boys come inside covered in sand and mud. The only time we ask them to stay clean is when we're about to go somewhere in the van and we don't want the van to be covered in mud too. Otherwise, whatever they are wearing is fair game for whatever they are doing. Ours come in with rips too.
We live on a farm in the wilderness.
When the three older ones were infants, they ate wearing only diapers. A quick sink bath each and dressing in the clothing from before the meal and we were off. Now they are older and don't tend to spill their food as much, but they do find all sorts of ways to be filthy by breakfast time.
If it's very muddy outside, they put on slush pants over their undies and then hang them to dry so that we can just bang off the mud for later use. They hate the feeling of slush pants over pants.
With blueberries, I put a sleeveless undershirt on our youngest for the duration of the meal, so that I don't care at all whether that comes out in the wash. Naked would be fine, but it's too cold up here for that except in the summer, when they all like to be shirtless anyway.