most experienced developers don't have a portfolio because they code for a living lol
My portfolio site is just one of the sites on my personal website that also hosts many of my projects. It wasn't much work to setup, and it provides organization and sharing capability so there's motivation to make it anyways.
I'd argue that that is indeed the majority. Maybe they have some work from school days, but very few devs are making portfolio pieces years into the industry once they can flesh out their "Employment" sectiion.
IME you only need a portfolio as a non-junior if you are making a lateral move.
So most people with young kids then