Probably because for most of us they never existed - and yes, of course I mean "pre-agile".

This whole "before Agile it was all waterfall and no one could conceive of anything differently and oh my brothers, let me tell you what a nightmare it was" cant is just that - a cant, something people like to repeat without thinking about whether it has any actual validity in, you know, actual reality. In other words, a myth.

There have always been good shops and bad shops; but like the sibling commenter said, (in the better shops) people have been working iteratively for decades and decades before the Agile Manifesto descended to earth on a ray of light, accompanied by angels.

But where agile really shines is when the problem is poorly understood and the solution not well defined.

Which problems people, again, had already been solving for decades and decades before the AM.

Such negativity

"Negativity" is not only an appropriate, but a healthy and necessary response to the never-ending stream of cargo-cult tripe and talking point nonsense that is Agile.