Why build an entire computer on breadboards?

I think this is good advice. It reminds me of the advice about that the difference between a hoard and a collection is the display case. It's great to have the interests and you like what you like, but if it's just a never ending pile that is damaging other pursuits it's no good for you, but if it's something you can catalog, explore, curate, and especially share in a meaningful way then having that interest is important. Even if no one cares about your display case but you. Also, OP, maybe look into building an operating system from first principles like that dude who made the tetris OS [0] or look into creating a nice collection of curated OS VM snapshots that demonstrate the things you're into in a running environment with tools like LXC/LXD [1] ( these days it's surprisingly easy to share VMs running with very detailed emulated specs running connected to a web browser) or look into taking the time to assemble one of those kits that lets you build a historic processor with LEDs and transistors on a bread board [2]. Or if you just like reading about it, even just keeping a journal or private wiki will I think make it so it gains personal context. Also, you like what you like. If it's not really hurting you to have a hobby about loving the history of OSs, I know some folks that are pretty encyclopedic about the inside baseball of pro wrestling or star trek. Hunt your bliss. For what it's worth, I'm pretty sure your insights into the things your reading is something I'd enjoy

Ben Eater had a whole video on why he encourages building a breadboard computer. ▶ this video A lot of people have taken what they've learned and moved on to designing their own PCB versions. You can see some of them here: link

I got caught up in all his videos and had the same question. Fortunately, he has a dedicated video where he answers this with testing on the scope: ▶ this video tl;dr is what the sibling comment already explained: low clock rates.