Why can I mirror my iPad on my Mac but not use the same iPad as an extension display to my MacBook M2 (2022)?

Both devices are in the same wifi and I would love to use the iPad (8th gen, software version 15.5) as an additional screen to the Mac (OS 13.3) but when I go into settings, I cannot find the sidecar setting to turn this on. Conversely, mirroring the iPad on the Mac works flawlessly. Any help would be very much appreciated. Thanks!