It's not about asking them how to design a chip, it's about them providing the tools needed to go from a Verliog design to something they can manufacture.
So I would say to that extent they do, the foundries provide dev kits with cells to use on their process, and there's definitely the same incentive, good reusable IP gets you products faster which gets them more business. I think a lot of the landscape is just driven by the sheer cost of getting it wrong. Spinning a pcb is a bummer. Needing a new mask set is so much worse.
There is eFabless, among other efforts in the vein you describe, they do a multi project wafer shuttle thing that google sponsors using skywater. It's supposedly an open source PDK, I haven't used it.
