The above two comments show the difference between software "engineers" vs "developers"...and none of the major social media platforms (and other consumer-level applications) employ engineers.
Other projects can't use waterfall development because they would like to actually produce something useful instead of what was decided at the start of the project.
This isn't the way pharmaceuticals are developed; we don't require the pharma companies to know how they work (and we shouldn't, because we don't know how many common safe drugs work). We validate them by testing them instead.
Other projects can't use waterfall development because they would like to actually produce something useful instead of what was decided at the start of the project.
It's a whole different world of software development. If you set out to build flight control software because it is needed to run on a new airplane, you're not going to pivot midstream and build something else instead.
