A few years ago I was playing with hidden files (yes, that was a dumb move) and I accidentally deleted an important symlink.
The result: My mac didn’t want to boot anymore. I let you image how freaked out I was. A lot is an understatement.
Luckily I had a 1 week old backup on my external HDD and booted from it. I dived into the finder and found what I deleted (just one single file) and restored it. Rebooted and everything was fine. If I didn’t have it I would have been forced to either do a clean restore or try to figure it out manually and it would have been a huge inconvenience. Basically, at least one full day wasted, probably more.
Most people get a backup after they experience a catastrophic loss. Don’t wait until that point!
The barrier to entry is pretty low nowadays. Black blaze, for example, offers off-site backups for 5$ a month, or you can buy your own HDD for relatively cheap (this post is in no way sponsored, I just use them and they worked well for me) and use something like Carbon Copy Cloner on it. It’s surely worth more than the data you are eventually going to lose if you decide not to back up (yes, a decision not to do anything is still a decision).