The wheel trim that it is holding on is likely damaged, so a previous owner has added the cable tie to stop it falling off. The damage may not be visible from the outside. There are plastic tabs on the inside that are pressed against the rim by a metal ring. One of the plastic tabs may have broken making it a bit loose.

It is possible that someone has added it to make it a little more difficult for someone to steal them, but that is less likely.

The wheel trim that it is holding on is likely damaged, so a previous owner has added the cable/zip tie to stop it falling off. The damage may not be visible from the outside. There are plastic tabs on the inside that are pressed against the rim by a metal ring. One of the plastic tabs may have broken making it a bit loose.

It is possible that someone has added it to make it a little more difficult for someone to steal them, but that is less likely.