Who decided that archive & backup are the same thing?! I don't know who decided this, but I've seen it for years. I'm guilty, I jumped on this bandwagon. We've made it like some fast food combo deal or something. This is terrible because they are two very different functions.
Backup is your insurance plan! The other day one of our developers came to our meeting and told us his laptop had went down and wouldn't boot back up. Our immediate response was "Do you have a backup?!" Luckily his system backs up to Onedrive every day so all we have to do is get him a new laptop, have him do a recovery and boom he's back up. See what I did there?
So that's why a backup is your insurance plan, it makes sure you're covered when something goes wrong. It makes sure that your business, personal files or whatever you need to backup doesn't suffer when technology fails or somebody makes a mistake. This could be a lot of different things:
Bottom line if you have access to data today then tomorrow you don't that's what a backup is for.
Now an archive is a very different thing. We all love to hate LTO but it still is a really valid archival format. A few years ago I spent about 30 hours scanning family photos, I made a photo book and sent it to all of my family, but once I was done I didn't need those files taking up space on my computer. I still need these photos, I may eventually need to get back to them.
That's exactly what an archive is for! When you're done with a project and you know that you may need to access this for years or possibly ever. But you know that you definitely don't want to delete it. That's when you archive it and set it on the shelf.
What I love about LTO as an archive format is that I know if I need these files in 5-10 years, I can grab this tape and recover them with no problem. If I had thrown these on a USB drive and put it on the shelf, I wouldn't be so confident.
So when you're deciding between a backup and archive think of what the use case is.