Mere Exposure Effect
Sometimes, people will trust a UI element more if they've seen it before. This is typically coined as the "Mere Exposure Effect", because merely being exposed to something is enough to make it seem more trustworthy.
Take a look at these buttons. How do they feel? I'm willing to bet that they are instantly recognizable, and you don't even need to read the labels to know what they do. This is because these symbols have been shown to you so many times that you have been conditioned to associate them with "save", "send", and "cart".
It's funny, despite the fact that we have moved on from floppy disks as a medium, the icon for "save" is still eternally pinned to the floppy disk. When we send things, we don't literally fold our paper into an origami airplane and throw it at the person recieving it. The only one of these icons that actually makes sense is the "cart" icon, but even then, it's not really a cart. It's just a little table of data sitting on your computer.
So what would happen if we tried some new icons?
Now this is a bit more difficult. You can technically read the labels, but they don't seem to make much sense. Even though the labels are the same, and the icons are technically "correct", they don't feel right. This is because they are using unconventional icons that go against your cognitive associations.
We use hard drives to store our data, but usually the icon for a hard drive refers to accessing the root of the filesystem. We use email to send things to people, but the icon for the email app is usually a little envelope, not the act of sending itself. The last one is just hard to parse because it isn't actually a cart, it's just another shopping-adjacent symbol.
These "conventional" icons are the backbone of how we interact with our modern technology. The cognitive associations are so ingrained in us that we can recognize them instantly, even if they don't make sense.