A Pet Peeve Addressed
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Why Don't All Food Cans Have Pull Tabs?
"Cans with a pull tab are more expensive because there are more steps to the manufacturing process. First, the end piece has to be scored with incredible precision. "The tolerance we run on our metal packaging products," which is the "permissible variation" in product measurements, "is in microns (one-thousandth of a millimeter)," says an exec. The scored end needs to be strong enough to hold the contents inside — often under pressure — or to withstand a fall from the store shelf, but the lid also has to pop open easily when the tab is pulled. That's why DRT's machines are tuned down to the micron."
More: https://money.howstuffworks.com/food-cans-pull-tabs.htm