You never know what could happen to your Mac laptop! Let’s imagine you are out of town (or at home) and working on a big project, and you accidentally crack your MacBook Air screen. What would happen if your screen were dark and you could not see any part of the screen?
If you’re not backed up or if you’re not traveling with a spare backup, it’s not going to be easy to attach your unit to a monitor; add a keyboard and mouse as well as a backup drive to grab your data while you are traveling. This might be tough even if you are home! This is why I carry a small, encrypted SSD Time Machine backup when I travel. If you can borrow a Mac, you can plug it in to access your data. Also, you should carry your Time Machine drive in a hidden jacket pocket, so if your backpack is stolen or lost, you have your most recent backup from last night.
Note: I recommend that you have TWO Time Machine backups. You cannot have too many backups! I like having one that always stays home and one that I always carry with me. Both should be encrypted and password protected!
Here I am using Time Machine to create a new backup pre-repair for a new customer. As you can see, their screen is cracked, but there is still viable enough to see their data and complete a backup!