The thing with zero bugs is that software is very complicated not due it being harder than hardware but by simply that get some devs, POs, sys admins, devops and stuff and zero bugs will be defined entirely different.

For example, in theory the only real system with zero bugs would be one you use exactly always the same way, at the same place for the same exact goal and never change that.

Its a bit related to the old saying in cybersec " the msot secure system is the one who isnt used at all and not connected to anything" so basically a tradeoff with UX always. But who would want that?

I think thats why software on more actual mission critical systems are way more stable and bug free... still hate the word. Because it cant be avoided, since you see bugs sometiems are just situations when your uncontrolled actors (users, other services) use the system in a non-intented way so you try plan for that such us retry mechanisms, logging, backups etc.

Because when we further think about it, have you ever witnessed a system in real life thats bug free? Humans have bugs all around, buildings, cars, even nature. So how would you expect we could do that, esp each random company? Also do we want that? What if we said there is a 100% defiend system we can make perfect in 100 years... Good, but whats the point?