I keep hot shoe covers on cameras, though they have only minor use these days. Long ago in a galaxy far away there were rather important. Today, they serve to help keep the commonly present activation switch (see below) clean and reduce the likely hood of a strap, part of a bag, or clothing from snagging on the hot shoe.
Hot shoe covers were introduced shortly after accessory shoe evolved into hot shoes having a flash contact. In those ancient times flashes presented rather high voltages (300-500v) at the sync contacts, cord or foot. When a camera has both a PC terminal and a hot shoe, connecting a flash to one would make the voltage present at the other unless some steps are taken to disable the unused connection. Initially, most manufacturers simply put an inexpensive plastic cover in the hot shoe and sometimes a plastic plug on the PC terminal. These severed to prevent you from brushing the unused terminal with a finger or nose and getting an uncomfortable shock.
After a short period, many manufactures began putting an "activation switch" in the hot shoe. This would switch the hot shoe one, and the PC off in a few cases, when a flash foot was inserted. With these cameras, the hot shoe cover is of no use other than what I mentioned in the first paragraph. There were a few other designs, such as the Canon Canonette QL17 GIII which had a swinging cover over the PC terminal to disable the hot shoe when a PC cord was used and to cover the PC terminal otherwise.
These days flashes use a safer low voltage and the shock protection is no longer an issue. Still, some cameras, like my Nikon cp8400, have a switch in the hot shoe to sense the presence of an external flash. Using the cover to keep this switch clean is a minor, but reasonable, thing to do. The camera also slides in and out of a tight pouch easier with the cover in place.
There was a period when Canon added some small tabs to their hot shoe cover for the "A" series cameras (AE-1, ... and maybe the earlier EF). These tabs allowed the hot shoe cover to also serve as an eyepiece cover. A nice idea. Eyepiece covers are valuable when you use the camera's light meter without having your eye up to the eyepiece (they are of no use "during the exposure" as is often stated). When using a manual camera that, like many of the early Nikons, have an external meter display you need to cover the eyepiece when using the external display to avoid having light entering the eyepiece and influencing the meter. Similarly, if you are using an auto exposure camera in automatic you need to cover the eyepiece if you shoot without an eye to the finder since the meter will be setting the camera for you and could be influenced by the stray light.