That's nonsense. DCA is an investment strategy that solves the need for investors to know when to enter the market. It has nothing to do with being a high or low-income earner.
Anyone with a low income could still afford to buy a small fraction of Bitcoin (that they can afford) without the need for cost averaging.
If you're going around telling people that the DCA method is the only way they could invest in Bitcoin - stop. You're not telling them the truth.
And no, DCA is not a magical fail-proof strategy that guarantees profits, nor is it the most profitable one. It's just convenient and easy to grasp, that's all.