I also think this comparison is made by people that have never been involved in construction projects. Even something reasonably small in scope like rebuilding a house is still an exploratory process. Redoing ours we found the frame was no good and had to go back to get planning permission to build a new top structure. Even now we're getting our lower outer wall repaired (basically the only part of the structure that's actually original now) and the initial cleaning showed there was more work involved. So we renegotiated the cost with the builder.

Then you look at big civil engineering projects that seem to always be over-time and over-budget.

The treatment of estimates in project management for software is way more like the assumption we have an assembly line where even if there are issues these are routine enough that they can be padded in. The problem is that software is an exploratory process and not an assembly line.

It's even worse the more creative the project is. I've worked in games for fifteen years and I don't think it's possible to estimate when a game will be 'good'. Making one is a process that requires a lot of feedback, iteration and scope management. It's part of why we see so much reflexive crunch as the reality of making a game hits poor project management strategy based on this assembly line thinking.

The words Gantt chart make me shudder.