Why is there a jumper wire between the hot screws on my outlet?
Someone broke the fin off, then had breaker's remorse

A factory-new duplex receptacle has a copper "fin" connecting the two screws on each side -- breaking this fin off on the hot (brass) side is done when you want a half-switched receptacle outlet, for instance.  It appears somebody broke the fin off at one point, then either the same person or a different person had regrets about the broken fin and replaced it with a jumper wire.  So, leave the fin on your new receptacle, and all will be well.