Not just RAM and SSD. Displays can break. Power ports can break. USB-C ports can break. Keyboards can break. PCBs can break. And those take time to ship if you have a Dell, HP, Framework or even an Apple machine. I like being able to walk to a nearby store and grab a new MacBook Pro in case I quickly need a new machine to continue my work. My clients typically hire me for short periods and they need me to work at full capacity for that time period. Waiting a week while Framework ships me a new display is not an option.
A Time Machine restore has never failed me. You are fully operational after the backup is restored. Syncing your data onto an SSD via M2 isn't comparable.