I already have a workstation PC + Raspberry PI cluster at home. The problem is availability. I cannot guarantee that I can access the home machines from anywhere at any time. The internet or electricity could stop working at any time from where I live.

Imagine, I am running a trading bot at home. I might lose some money when the home internet is down and the bot cannot react to the price change.

I might want to try a new VPN software. I don't what to try it on just a local network right?

There are many use cases to use a personal cloud server over a local machine.