Ok, so it's not really that you're not checking error codes. It's that you can write stuff like

   ok = whatever().

If whatever is successful and idomatic, it returns ok, or maybe a tuple of {ok, SomeReturn}. In that case, execution would continue. If it returns an error tuple like {error, Reason}... "Let it crash" says you can just let it crash... You didn't have anything better to do, the built in crash because {error, Reason} will do fine.

Or you could do a

   case whatever of
      ok -> ok;
      {error, nxdomain} -> ok
   end.

If it was fine to get nxdomain error, but any other error isn't acceptable... It will just crash, and that's good or at least ok. Better than having to enumerate all the possible errors, or having a catchall that then explicitly throws an eeror. It's especially hard to enumerate all possible errors because the running system can change and may return a new error that wasn't enumerated when the requesting code was written.

There's lots of places where crashing isn't actually what you want, and you have to capture all errors, explicitly log it, and then move on... But when you can, checking for success or success and a handful of expected and recoverable errors is very nice.