Zimmer was a genuinely excellent defender (90th percentile in 2021, the year prior to his acquisition) with elite speed (94th percentile in 2022), so at the very least he had two skills that at the time were sought after given no one else on the roster was as good of an OF defender (we had absolute plugs Gurriel and Teoscar out there) or as fast a runner.
Lukes is arguably not even as good of a defender as present day Springer, let alone KK and Varsho, and runs completely average. For comparison's sake, Davis Schneider is as fast as Nathan Lukes, Ernie Clement is 76th percentile sprint speed.
If all you want on the bench is a burner to run for Kirk in key spots, then you might as well call up Cam Eden who just swiped 53 bags in AAA only getting caught 4 times. He also can cover CF presumably adequately at the least. If you want another lefty bat that is a legitimate PH option and occasional spot starter, that's what Horwitz, Vogelbach and now Votto are competing for.