The problem is that low-income people often struggle to make ends meet, as any unforeseen expenses can push them over their budget when they no longer have spare cash to invest and their DCA purchases become inconsistent.
Knowledge of investing is always a good thing, but investing itself is not a universal, fit-all solution. People with low income should be primarily focused on increasing their earning potential (aka investing in themselves) rather than investing small amounts in assets like crypto or other markets.
When you don't have much to invest, even hitting great returns won't earn you life-changing money. It often creates a false sense of "having something going on" for you and makes you content with your current situation, whereas spending even a few years on getting real-life skills and increasing your earnings would elevate you to a higher level much faster.