Never advised by whom?

Investing is not concerned with getting interest at all.  Investors seek

Capital Gain,

adequate yield,

liquidity and

safety of principle.

Capitalism is based on investing borrowed funds. What you are really doing is turning wages into capital, by paying off loans used to buy securities.  "After borrowing the amount intended to be invested during the period, the saver invests the loan-proceeds.  By putting the "savings," out of reach, the borrower is forced to pay off the loans out of current earnings, which completes the saving process."