Why circuit people don’t design layout also in the VLSI domain?

I’ve asked the same thing when I started in VLSI — like, why can’t one person do both circuit and layout design? From what I’ve seen, it mostly comes down to specialization. I work more on the circuit side, and honestly, it takes a lot of time to optimize transistor sizing, meet performance targets, and run simulations. The layout side is a whole different world — you have to follow design rules, worry about parasitics, do DRC/LVS… it's very detailed. So, usually in the industry, you have separate layout engineers who are experts in that area. It makes the whole process faster and more efficient.