The problem isn't actually not being able to invest, it's not being able to meaningfully invest.
If you have $10, you can throw away. $10 doesn't mean that much to you. So let's say you sock it away into a decent stock. Let's get edgy. Let's pick something that's going to double in a year. A year goes by, you have $20. Now you can really afford that carton of eggs.
Investing at poultry levels doesn't mean anything to you because it's not enough money to do anything with. You generally need to be socking away 10-30% of your income to get anywhere significant enough to retire.
The argument that you can invest because you can afford to spend $10 is as useless as investing $10.