Do you know why construction projects don't get huge last minute changes very much? Because every change request is a billable event.

Software companies don't do this much. I've worked at only one that charged for changes, and -- surprise -- such changes were very rare.

Yup, in fact this is the strategy for profit maximisation for many, many construction companies. You look at the plans/requirements and if you spot loads of missing things you bid a low price with high prices for changes and make loads and loads of money.

Source: this is what my Dad did for a living, and I spent a couple of years doing it in my twenties.

It is also the strategy for profit maximisation for many, many software companies. "Change request" is a big deal in outsourced enterprise software dev. It is so bad that 'honest' software development groups that estimate accurately and don't have a culture of change requests cannot compete.