It's impossible to rely entirely on investments for our livelihood, except for those who already have unlimited assets and are maximizing returns. Other income preparation is necessary to meet living expenses so that investments don't impact performance. Bitcoin has cycles, meaning that for certain periods, we may only buy and not sell, and how can someone maximize their needs in such a situation?
Conversely, relying on short-term trading doesn't always guarantee sufficient profits to meet your needs. People think trading will make money easily, but in practice, it often doesn't work out as expected.
It is vital to have other ways to earn money for your living costs because investments are mostly for growing your wealth over time not for immediate spending. Bitcoin price goes up and down meaning you mostly have to hold onto it for long time so it is not good for paying bills right away. Also thinking that short term trading is easy way to get rich is wrong. It is very difficult to make steady money from it. This all shows how important it is to have mix of ways to earn money with stable income for daily needs and investments for long term growth while understanding their real risks.