I quit work at age 39, 15 years ago. I will say that my thinking has evolved a quite a bit over the time. So I think the running away question is a good one, and I am not sure I would have thought so until age 50.
The realization that you are FI has such a profound impact on your attitude about work, that to be honest I have a hard time taking criticism of early retirement by folks who aren't there yet seriously. It is one of those life changing moments that you have to experience to appreciate it.
For the sake of argument lets assume that money issues aren't a factor (obviously not true for many folks hoping to retire in their 30s).
Even though I had achieved FI by 39, I wasn't sure about actual retirement. I'd hoped to find a second career. Hell I even offer to work part time for a start up for stock only this summer. But hope is not a plan.
A while ago I posted this phrase which seem to resonate with a lot of folks
"Your best months working will be better than your best months in your retirement, but your worst months in retirement will be much much better than your worse months working." Lower highs but way higher lows.
Now some people have jobs that are almost never fulfilling. Others have jobs which are inherently meaningful (I am thinking about things, like teacher, doctor, firefighter, Disney Imagineer, and entertainer). The rest of us have jobs which can be fulfilling depending on our attitude and circumstance. Personally I generally had interesting jobs. I was always very conscious that I was working for a very important company in its hey day. There were definite times that I realized that what my team did would have a small impact on hundreds of millions of people, which was pretty heady stuff.
I think as a society we are conditioned to look for way to be part of a larger organization early on. For example the emphasis on TEAM (there is no I in team) sports in schools. Good organization emphasis the team aspect (nobody left behind, my brothers in blue). Team building exercise are common in corporate America. In my experience good corporation don't need this they have a mission which everybody buys into. For example I bet that virtually everybody that works for SpaceX is inspired about establishing a Mars colony.
Still at some point, I think most everybody gets tired of taking one for the team. Instead they start asking when is my turn to get the ball and have all the other guys block for me so I can get across the goal line. Most of us realize that most of the potential blockers are asking the same question. At which point we start to plan our escape.
A part of Senator McCain standard stump speech is a call to "commit to serving a cause greater than your self-interest.". I think most people get a sense of purpose in life by doing exactly this.
Of course there are some who don't feel the need to do this, but I suspect that is minority. For them setting personal goals, earn a PHd, qualify for the Boston Marathon, travel to 50 countries, create the best cabbage patch doll collection in my state are sufficient.
There are plenty of ways of serving a cause that have absolute nothing to do with a job. For many people being a good or even better great, dad, mom, husband, wife, daughter, or son are fulfilling. A good citizen seems rather bland to me but it may suffice for others. Still another message we get is that being a stay at home mom isn't enough, much less a stay at home dad.
Charities, civic organizations, and causes all are worthwhile activities to find the sense of teamwork that a job provides. Still my experience is that most volunteer activities are rather mundane: clean up a park, read to kids, give tours, help with fund raisers. For the most part entry level jobs with some nice perks and for a good cause. I estimate that less 20% of volunteer really get into the activity. Jobs for most people provide that sense of team and being part of cause greater than your self interest, which fills a need. Getting a paycheck provide a sense of validation that volunteer jobs don't generally provide.
I think it is worthwhile for young retirees to ask the question where will I find that sense of fulfillment and self work that working provides. I suspect that by the time most people hit their 50s and certainly by the time they get into their 60s they have accumulated a lifetime of validation, and idealism has been replaced by cynicism.