Okay I am not the most savvy while dealing with high guard but are the example vessels meeting the required crew requirements?
High guard pg 23 by my reading which may be wrong indicates that a minimum crew of a civilian starship consists of the following
1 pilot
1 astrogator
1 engineer
1 maintenance
1 administrator
1 sensor op
1 medic
1 officer who in a civilian vessel also acts as the captain
for a total of 8 crew.
Many of the civilian vessels don't meet this requirement let alone exceed it. The lab ship crew is listed as pilot and astrogator for a 360 ton ship. Maintenance crew on is first mentioned for a civilian ship with the subsidised liner a 600 ton ship. Are the designers rounding down (I was told quite firmly in another thread that I should round up) or are the designers playing loose and fast with the crew rules?
As I see it, those are roles, and not necessarily individual positions that must be filled by an individual. The reality is going to be that automation takes a lot of the skut work away from crews, and automation requires a bit of attention as well.
For small ships, especially non-military ones, it is not unexpected to see no one manning the bridge 24x7. Sensors will alert them to incoming hazards (or at least known ones that can be detected). On a military ship I'd expect a watch to be conducted on the bridge, in engineering and probably in the weapons control section. Everything else is subject to change based on what is happening on the ship. Smaller ships, like a Scout, may see their bridge fully occupied only during jump re-entry, or scanning of planets up close and everyone is curious. Otherwise the systems will do the work and they just need to monitor them and provide oversight (or else review the sensor data to look closer at things of interest).
In theory a pilot can double as the navigator and sensor operator. The engineer can double as the maintenance guy, and maybe the medic is the admin. Anyone can wear the captain's hat. However.... when things get busy it gets harder to do multiple jobs. Piloting the ship and evading incoming fire makes it harder to read the sensors and plot the jump accurately. So as your time is focused on other tasks your chances of mistakes increase in the minor things. That can be easily accounted for in die rolls with additional difficulty in successful rolls, depending on circumstances.
You are also going to see smaller, less professional ships (i.e. the ones full of PC's) going slack with certain things. Think of the episodes on Firefly where they ran parts down to the bone (and then some) because they had no cash to buy spares. Or when they were all at the dinner table and nobody was on the bridge. Episodes like that are likely to be handled more by PC's than by professional crews (pirates might be professional rogues, but they would most likely lack a sense of formality due to their chosen profession).
There is a lot of wiggle room here to make things different and fun for all involved (including Evile GM's rolling dice and cackling evile behind their screens... for no apparent reason!)