[tylerjl]

It's a good question, and a very mature/well-engineered Docker dev environment probably gets you near-parity with an equivalent nix setup. That said, my reasons are:

- Although not _all_ of our projects need nix builds in the end, at least a few do, and acquiring their devshells is essentially zero-effort (you just ask nix for the devshell for the package instead of the package output itself)

- As some other commenters have noted, dealing with large container contexts can get hairy/slow. A devshell just tweaks a few environment variables, which is less of a tangle when working on the various projects (I use direnv, so my emacs session hooks into `flake.nix` and finds everything in-path automatically)

- While you could get a bit-for-bit identical dev environments by pushing a built container image to a registry that all devs pull from, I think most people would write a `Dockerfile` once and let folks build it locally before hopping in, which leaves a small (but extant) possibility that some environments may be subtly different (shifting container tags, ad-hoc apt-get commands, etc). A flake.nix coupled with a flake.lock means all devshells are lock-step identical.