How much is the data on your computer worth to you? If that’s a difficult question to answer, let me rephrase it: how long would it take to obtain the data on your computer if you lost it suddenly, and what is that time worth to you? It’s worth investing at least that much in a backup solution.
A lot of people will not have much critical data on their system. Maybe photos that hold sentimental value and a couple of documents they’re working on, but nothing catastrophic. These days, chances are those photos are synced to a cloud backup solution like iCloud or Google Photos. It’s…an okay solution. Not great, but it’s something. Many people don’t even have a cloud backup solution. Then their hard disk dies and their photos are gone, and they’re upset. Or they’re working on the next great revision of The Pepperwood Chronicles, and are a victim of a ransomware attack. All of this is entirely preventable. A backup is not a lot of trouble to maintain, but it saves you from a world of trouble when your data is gone for whatever reason. Think of backup like insurance or savings: you hope you never have to use it, but you’re glad to know it’s there. If your data isn’t backed up, you don’t own it, you’re leasing it from fate.
If I still haven’t convinced you that you need a backup, consider that most backup solutions are cheap or free, and maybe that will incline you towards it. The general recommendation is the 3-2-1 rule: at least 3 copies of your data in at least two kinds of media, and at least one copy must be offsite. The first part is pretty simple; the second part means that if one copy of your data is on your laptop, making a copy of it in a different directory does not count as a backup. If you have one copy on an external hard disk, that would count, but another copy on a second hard disk doesn’t. This is because your backup can also fail: hard disks can and do fail over time, sometimes without warning. Further, there’s the issue of bit rot, so multiple backups on different media is a good idea. The offsite backup is for catastrophic cases: your house burns down, you took your data with you on a cruise and the ship sunk, that kind of thing. A less extreme use case is that you want access to your data from a different device–an offsite backup is a great way to achieve this.
Your backup solution is your own, but I will share mine. All my files are on my laptop or on iCloud Drive (copy #1). The files on my laptop are backed up using Time Machine to an external SSD, and the files in iCloud are backed up using rsync to a second SSD (copy #2). All of this data is backed up using Backblaze B2 to their cloud (copy #3). Backblaze runs in the background, automatically backing up data for me, and I run my Time Machine backups about once every 10 days. In the worst case, my backups are 10 days out of date, which is still better than being nonexistent.
There are alternatives, of course. You could use a cloud storage solution like Google Drive or Amazon S3 for your offsite backup. You could use Carbon Copy Cloner instead of Time Machine. If speed isn’t a priority, you could use external HDDs, which are usually cheaper per GB.