Because complexity is boundless and in software it has no cost. Building a house will have a restrictive initial budget for complexity, you don’t have enough i

Because complexity is boundless and in software it has no cost. Building a house will have a restrictive initial budget for complexity, you don’t have enough in that budget for rotating floors, or an elevator that is catapulted to the correct floor, etc. These would cost both at engineering time and implementation time a huge amount. Less complexity is easier to analyze. In case of software, complexity has negligible cost, relative to physical systems. You can increase it ad infinity — but proving it (the whole stack - from the hardware-OS-userspace software) correct is likely impossible with even the whole of mathematics, in certain cases.