This just isn't automatically the case.
If you have a dream job that fulfills you in every way and is nothing but a positive (I've had three such jobs), you still need to eat, pay bills, etc. So you still need to be paid for it.
How positive or negative the job is doesn't enter into whether or not people need to be paid to do the job.
There are no alternatives
You get hired to work on a small team, but soon enough you have 2x the responsibilities but you only get a small raise. Or you are hired as a technical person but very quickly you are pushed into managing teams and learning the rest of the business. All of this is adds up and it feels like you were hired to do X, but now you are doing XYZ, just because if you don't you lose the job or don't get a small raise.