What retained earnings aren’t
To put it bluntly, retained earnings are not money in the bank. As companies generate net income (earnings), management will then use the money for all of the things (and more) listed above. Most companies must continually reinvest at least some portion of their earnings to remain competitive and profitable. Old assets have to be replaced and modernized, and companies are often caught on a treadmill of spending.
Back to Apple as an example: It's one of the most profitable companies on earth, but it has had to constantly spend on research and development, and its manufacturing partners have had to retool their factories almost every year simply to remain viable. This is paid for by retained earnings; ideally, it generates more earnings than it costs to deploy, but the assets are depreciated as they lose economic value.
So retained earnings isn’t money in the bank, and it's also not the liquidation value of the company. It's just a running tally of how much a company has earned over its lifetime, after dividends paid (and stock repurchased and retired).
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