Employers may want to believe their workplace really is
like a family, and, in that moment, they may convince
themselves it actually is like a family.
1) An employee can actually do a 9-5 job AND have a good relationship with their colleagues, have fun at work, and apply themselves - fanatical devotion is not required and should not ever be a criterion for judging performance.
2) However, the "bad" employees I hired (which was totally my mistake in the first place) did all have in common that they didn't care about their work at all. Some even consistently lied, about the work they had actually done, about how much they cared (unprompted), and about how they dealt with customers.
There is a fine line between utter disinterest and having a healthy work-life distance. I'm not surprised so many managers have problems categorizing this.