If you buy a loaf of bread, it comes in a plastic bag closed with either a metal twist-tie or a little plastic tab. Either of these may be re-used to close the bag again after you have used some of the bread.
If you buy a bunch of carrots, they generally come in a plastic bag that is closed with a little piece of tape. The tape is generally stronger than the material of the bag, making it really hard to remove the tape without ripping the bag open. And even if you do get the tape undone, it can’t be re-used.
Why do they do that? I’m not any more likely to use the entire bag of carrots at once than I am to use a whole loaf of bread at once, so it’s not that the carrots are less likely to need a bag closure.