The point of doing this as a ceremony rather than an afternoon of tinkering is repeatability and evidence. Devices are checked, seeds are generated offline, backups are recorded in durable form, receive and spend paths are tested, and every step is written down.
For multisig, the ceremony also fixes the wallet's descriptor - the information required to rebuild the wallet later. Losing that information can strand funds even when the keys survive, so it is documented and stored deliberately.
Recovery is then rehearsed rather than assumed: signing with the intended quorum, verifying balances, and confirming that the documented steps work when followed by someone else.