There are plenty of reasons why engineering isn't "agile" and it's only usable in software development, and one of the main reasons is that software development projects manage a single resource: man/hours. Building the wrong or inadequate solution has its cost, but rebuilding something from scratch does not require additional resources to be allocated to the project: just keep the same team working on it and results will pop up.
Engineering projects are very different than software development projects. Materials and components are the driving cost of a project and there are plenty of stuff that must be done right from the very start. It's unthinkable to scrap a machine or building or tunnel midway through, and it's inconceivable that some disaster happens at all. Engineering either gets it right at every single stage of a project or there are serious consequences to deal with, which in some cases might even be criminal charges. If for some reason a prototype crashes during development then the project might be forced to shut down.