This misses the actual advantages that a managed service provides, like the fact you don't have to worry about the stuff you mentioned. Does your solution scale to multiple cameras? Will you get push notifications when movement is detected while you're on holiday? What if that very laptop is stolen? Would be ironic.

I'm not saying your solution is bad, my house has the same thing (with 4 cameras around the house), but most people don't want to spend time managing yet more stuff, and debugging their camera system if something goes wrong.