I think the idea that nobody would volunteer for a deep space mission if it meant being away from families is a good thing. Separates the wheat from the chaff. In other words, those who do it have uncommon courage or dedication to the mission. Shouldn't stories feature exceptional people and not Joe Average???
I don't buy that at all. We're talking about a long-term scientific and diplomatic mission involving lots of first contacts with alien races. That's not the kind of job you want to give to tough guys who pride themselves on their ability to sever themselves from social and emotional ties, or to introverted, closed-off geniuses who wouldn't really be concerned one way or the other.
And how is being part of a family or community incompatible with being exceptional? Lots of works of fiction are about exceptional families. The Fantastic Four are a family led by one of the most brilliant men in the world and one of the most powerful, wise women in the world.
Lost in Space was about a family of space explorers in which nearly every member was a genius in one scientific field or another.
Eureka was about a small-town community of geniuses, many of whom had spouses and children who were as brilliant as they are, and even the ordinary sheriff was an intuitive genius in his way and had a daughter who turned out to be as smart as the supergenius Eurekans.
So to coddle them by bringing families along into the wilderness just seems wrong (not to mention reckless, if the final frontier is truly a dangerous frontier).
Macho twaddle. It's not "coddling" to recognize the fundamental human need for companionship and community. We evolved as a social species. That's how we're adapted to survive: as a group, not as a bunch of lone wolves.
And humans have been bringing their families into the frontier/wilderness for hundreds of thousands of years. How do you think we spread across the planet in the first place? And I've already expressed my thoughts about danger as a factor. Our kids are in danger of their lives every time they get into a car. Staying "safe" at home is only relatively safe. Good grief, even if you are safe inside your house with its locks and its lights and its security system, you can just go walk into the woods a mile or two away and be in mortal peril. Safety is a function of what surrounds you. And families inside a starship -- an explorer starship that isn't intended to go into battle except as a last resort -- would be surrounded by the most advanced defenses available to the Federation. It's only the crewmembers who went on away missions who'd routinely expose themselves to danger.
So how this played out was to limit the actual threat to life and limb of the Enterprise, so you lose the frontier aspect entirely in the process.
What defines a frontier isn't the amount of danger. What defines a frontier is that it's a zone beyond the boundaries of a society's legal control, in which new contacts and dynamic and complex interactions between different societies can occur. As long as the ship is discovering new life and new civilizations and having interesting interactions with them, the frontier aspect is very much present, even without constant violence.