Yeah, for sure. The only issue would be that I wouldn't be as interested in building an open source dishwasher for every possible (or even the most common) users/use cases, but for myself.
I don't think this is limited to just digital items like software.
I would absolutely use an open source dishwasher if I could ship my custom design to a manufacturer to build.
It's bound to happen at some point, right? There's a lot of people doing dishes.
No. As a hardware hacker myself, the benefit and draw is the fun of it, I don't want to have to hack my own dishwasher and make it work to my requirements, not maintain it.
Hackers usually write very bad code, in case you weren't aware