Doesn't that assume that you're sitting on a pile of cash already and deciding how to invest it? That's not the situation for working class investors who didn't inherit a lump sum or win the lottery.

The optimal strategy for most retirement savers is "invest it as you get it" which is basically dollar cost averaging except in the rare cases when a pile of cash falls in your lap.

Yes. That's usually how the term is defined. You have a lump amount to invest and you invest it over a period of time.

Meaning shifts, and now the term is also being used in web forums to describe the investment strategy of "in each paycheck, invest a bit of money." This creates confusion.