Floppy disks had stick-on labels. Optical discs can be written on with a Sharpie, or printed with special ink-jet printers, or round stick-on labels applied.
USB sticks have zero affordances for labeling. They are often bubble shaped or covered with rubber so you can't easily stick on a generic sticker such as an address label or file folder label.
Meanwhile, they are sold with color-coding to indicate capacity and USB generation, presumably to prevent mistakes at check-out for bulk non-carded products. This means that you tend to have a bunch that all look alike.
Beyond the question of how do I tell them apart... Why were they not designed to be labeled with a pencil, or sticker, or coding of any kind?
Sticking them one by one into a running machine to see what's on them is not going to work for boot images, which, e.g. this Mac Book Pro shows as "unknown" and un-helpfully offers to reformat instead.