With a job or a gig you are provided value/compensation for your efforts, can be in the form of BTC directly or Fiat that is then converted. Even in places of hyper inflation there are still fiat jobs that then people save in BTC. What you are simply referring to is being self employed more so then just only "earning in BTC". Again, my point is, based on your post, there is no fundamental difference between doing a job and earning BTC directly or earning a Fiat wage and converting your earnings by buying BTC with that wage.

Edit: Also, every person person currently alive will be dead by the time the last BTC is mined in 2140 or whatever. BTC is always available, it's just about what price in a Fiat currency you need to pay to get it. But again, BTC is a savings technology to save the value you create today for a future day, even if that value is 500 sats.