Adaptability, Flexibility, and Resiliency
The ERE lifestyle is much more resilient than the typical paycheck consumer lifestyle. The combination of saving a sufficiently large portfolio and acquiring a large skill set is key. Money is extremely useful, but no portfolio is entirely safe. The skills we possess bring a second layer of security and expand our adaptability. ERE principles teach people to be more resilient by needing less money to meet needs, diversifying income streams to maintain more than enough capital, and having the skills to be self-reliant when money is scarce or devalued. If society continues to prosper, the portfolio will carry the day. If it doesn't, it is likely that an ERE-minded individual will be a community asset when most people are used to paying others to solve problems.
ERE also affords a person the flexibility to take advantage of unexpected opportunities that present themselves. They may be opportunities to learn a new skill, income or job opportunities, or even charitable or political causes to which you want to devote some time. See Maximize Serendipity in ERE Article/Summary.