1. NOT HAVING AN EMERGENCY FUND
How can you have an emergency fund if someone does not have a good job and that is why it is necessary to prepare for income maturity so that it can be far more stable with fixed expenses for the needs of daily life.
Obviously the advice in the OP's post is directed to people who at least have any regular income allowing them to survive and have a little surplus on the top.
If one doesn't earn enough to meet daily needs, he should be focusing on finding a steady income in the first place and worry about all other things later.
2. NOT INVESTING
Not investing is not a problem but a person must have other financial plans, such as running a business or job that is more productive because not everyone is involved in investment but their financial structure can also be better than people who undergo investment.
By all means, investing in own business or investing in own qualifications/skills that will help you increase your earnings is also investing. And even if you're short of money, you could still invest your time (aka your most valuable asset) to learn something useful.