doas and */sbin/* commands

Ok, so I'm trying doas again (it's an on/off affair, I'm not convinced
of its benefits yet). This has me stumped:

   2+0 ~$ doas printenv
  DOAS_USER=itz
  HOME=/root
  LOGNAME=root
  PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
  SHELL=/bin/sh
  TERM=alacritty
  USER=root
   3+0 ~$ doas which service
  /usr/sbin/service
   4+0 ~$ doas service
  doas: service: command not found

I know it's trivial to just type the full pathname, but it's still
inconvenient. So what is happening here, and can I have the sbin things
in PATH for doas but not otherwise?

-- 
Ian