Investopedia

Your 401(k) Is More Important Than You Think

Not only are there strict rules about withdrawing 401(k) money prematurely, but your 401(k) could be the most valuable piece of your retirement income pie someday; most people do not have any other employer retirement plan. Today, they remain a popular choice for investors, as they offer a flexible, proven way to save for retirement. At the end of Q2 2021, (the most recent data available), 66% of all Americans participating in retirement plans were invested in 401(k) plans, which held an estimated $7.3 trillion in assets, according to the Investment Company Institute.

Source: finance.yahoo.com