Ask HN: Why do many developers use laptops like desktops?

So I've been looking to switch jobs and been talking to some (software development) companies. This is what strikes me as a surprise - many of these shops use laptops exclusively. From talking to them more it turns out they don't really move around that much and effectively use their laptops as desktops. I am used to heavy duty gear (dual 4K 27 inch displays, top of the line CPU, 32GB+ RAM, comfy peripherals, etc) - I have pretty much identical setup at work and at home. I also have an ultrabook in case I need to be mobile (doesn't happen often). Am I missing something here?