There are multiple ways to earn bitcoin! Actually everytime you would receive fiat money you could also get it in bitcoin. There is/was a service around where you could get your monthly payment from your job paid out as bitcoin or just a percentage of it if you want to (not sure if it still exists), or you could sell online services for bitcoin.

Then the obvious ones:
- Faucets
- Gambling
- PTC

As you can see, the options of getting bitcoin are limitless.