For one, you need to trust that they’re actually doing that. Free or basic consumer accounts might not have that protection. Data centre locations can also get cut off like we saw after the easy coast storms some time ago. They can also randomly flag your content as pirated or illegal and lock your account without notice or recourse. Google and Microsoft accounts can be stolen and you can be locked out of them, losing everything.

Services can decide to shut down at any time. Sure, Google and OneDrive aren’t tiny companies but for them business is business and one day they might just decide to pull out or at least raise prices unreasonably. I used to use copy.com and Crashplan, both of which disappeared.

Also if you need to retrieve everything, like after a PC crash, it’s a huge pain to download. It can take weeks and you have to manually set up small batches because downloads randomly crap out. If it’s after a disaster like a fire or storm when there’s no internet access, you might be stranded.

There’s also huge misunderstandings about backup services vs sync services (like most consumer cloud options). You might think you have backups when removing a local file deleted your online copy as well.

Finally the physical copy is just more peace of mind.