Back when I was a house HP, there was one HP tech on shift. The shift HP did all primary chemistry, release permits, daily instrument checks, rad monitor filter changes, and did all the secondary chemistry on backshifts.
The tech specs only required one person per shift to be qualified on radiation protection procedures.
When they wanted to put two of us on shift, I was livid. There wasn't enough to keep the one tech busy for half a shift as it was, and doubling up would mean that I would have had to work twice as many evenings, nights, weekends, and holidays.
I imagine that they do things a little differently these days. They probably have the techs doing routine surveys to keep them busy - something that they could be doing during weekdays. Routine surveys are not a really good reason to be missing your family life.