Those that invested Three years ago at some point got some profits and Bitcoin has gone pass that amount before it reversed. However Those that invest in Bitcoin know the risk factors involved, they've studied the volatile nature of the subject matter, hence it doesn't give them panic attack, a dip shouldn't scare an experience investors, just as it is always said, that dips are opportunity for you to accumulate more if you have the resource because surely the market will bounce back.
So if you choose to make Bitcoin investment your sole income generating asset, then that's your choice and it should be respected, if you choose to have multiple streams of income to boost your resource base, that's your choice too.
The most recent ATH bitcoin reached was $73k. Do you think buying bitcoin at $69k and selling it at $73k is a significant return when you have to hold it for 3 years and take on more risk than any other investment?
Investing in bitcoin has no fixed time, I can't know exactly when I will make a profit, so I have never considered investing in it as my source of income. For me, investing is investing and is completely separate from my main income. There is no guarantee that investing will always be profitable and stable, so considering it as a source of income, especially the only source of income is a bad idea.
By the way, does bitcoin bring you daily/weekly/monthly income? If you can't do that, I doubt you ever considered it as a sole source of income.