I think this is too simple. First of all, hardware people have high incentive to fully replace components and systems for many reasons. Replacement is also the only way they can fix major design mistakes. Software people constantly do fix bugs and design mistakes. There is certainly no strong culture to document or dig up former mistakes made, but it's not like they don't learn from mistakes, it's just a constant process. In contrast to hardware, there is usually no point in time to retrospect. The incentives to rejuvenate systems are low and if considered often seem expensive. Software engineers self motivation is often ill-minded, new devs feeling uncomfortable with the existing system and calling for something "modern". But if the time comes to replace the "legacy" systems, then you are right, no one looks back at the former mistakes and the devs that know them, are probably long gone. The question is whether we should ever replace an software system or focus more on gradual and active modernization. But the latter can be very hard, in hardware everything is defined, most of the time backed by standards, in software we usually don't have that, so complex interconnected systems rarely have sane upgrade paths.