Why do large organisations need to back up their data in different locations?

The simple answer is - security. It's no good backing up their computers, then keeping the back-up on-site. If the building is damaged by fire - they not only lose their equipment, but the back-up too. Lots of big companies put their data back-up in their bank's vault !

I run my own reptile business, and I would be devastated if I lost my back-ups. I store mine in a fire-proof safe - which is embedded in the concrete floor of my reptile 'house'. The building is separated from my house by about 200 feet.