Humans have been constructing houses and doing maintenance on them for a few thousand years, but we've only been writing software for a few decades. We certainly didn't reach out current process for framing houses in the first few decades of carpentry.

That being said, I assume that the first few decades of carpentry didn't undergo as many changes as software has in its first few decades. My theory is that software changes so quickly because it can be bootstrapped. When framing a house, you can learn from the process so that you can make the next frame better by changing the process, but the output of that process (the house frame) doesn't directly affect the next time you attempt it. On the other hand, you can write software that invents an entirely new process for editing software (e.g. a compiler or interpreter), which then you can use to write software that might not have been possible before. You can then repeat this process with the new software, creating yet another paradigm for writing software, and so on. More generally, when a process produces a tool that can then be used for to do the process in a new way, the process will be able to evolve much more quickly than if updating the process can only be updated with the output from other processes.