Why do I need cloud backup? I back up to an external drive every day.

Credit where due: backing up at all puts you ahead of many businesses. But walk through the failure modes of the external-drive routine honestly. It is manual, and manual routines get skipped on the busy days, which are exactly the days that matter. It is unverified: unless someone regularly tests a restore, you do not know whether the drive has been quietly failing for months, and drives fail without announcing it. If it is not monitored and tested, and daily manual backups almost never are, it is not a backup; it is a ritual.

Then there are the two failure modes that take out the original and the copy together. Ransomware encrypts every drive it can reach, and a USB drive plugged into the computer is the first thing it reaches; attackers specifically hunt for attached backups. And anything physical (fire, flood, theft, a power surge) treats the computer and the drive sitting next to it as one object. The whole point of a backup is surviving the bad day, and the external drive shares the bad day with everything else.

Proper business backup is automated (no human has to remember), monitored (failures generate alerts someone acts on), tested (restores are actually performed), and off-site with an immutable copy (ransomware and fires cannot reach it). Keep the local drive if you like; a local copy makes small restores fast. Just do not let it be the only copy, and do not let 'we back up every day' go unverified. Ask when someone last restored a file from that drive; the answer is usually the whole argument.