The design of a house doesn't change every 3 weeks while it is getting built. House construction is usually only started after a massive amount of detailed des

The design of a house doesn't change every 3 weeks while it is getting built. House construction is usually only started after a massive amount of detailed design and planning is done. This is priced in. This is almost never true for software. Even with the above houses often take longer to build than expected and unforeseen issues can arise. Even the weather can screw things up. The amount of unexpected issues that can come up in software is huge. Everything from a bug on a library that you use to differences in the exact machine that the software will run on vs where it was developed.