There’re 20 guys out on a single peak.
If you paddle out, you’ll go from getting no waves (if you don’t) to getting some, so dramatically increase your own wave count from zero.

Meanwhile, each individual in the line-up would get approximately a 20th fewer waves if everyone was sharing in turns (sharing in turns?!?); instead of getting one in every 20 waves, they’d get one in every 21.
This is a relatively minor consequence diffused among the existing surfers, and not easily directly attributed to the newcomer.

This sizey imbalance in the benefits/costs analysis promotes paddling out every single time, along with one other important thing.

Because you can.

Garrett Hardin’s famous 1968 paper, The Tragedy of the Commons* on the planet’s limited, shared resources (the commons) and their abuse by swelling populations (the tragedy) has been applied to various things down the years from world fisheries stocks to the welfare state.

The conclusion of his paper is that there is no technical solution to the population problem; instead it required rather changes in ethics or morality, as in what’s cool and what ain’t.

And while you mightn’t get many surfers to extrapolate the argument as Hardin did to indicate that certain sectors of the population should be discouraged from multiplying, if you look at some of his key arguments, some of them aren’t a million miles away from forces we see manifest themselves in our line-ups all the time, from midsummer main break free-for-alls to tire-slash secret spots in the woods to double gnarly localised island slabs and everything between, as the multiplying masses continue to join mankind’s migration back to the endless sea.

*The Tragedy of the Commons by Garrett Hardin was published in Science in 1968. Hardin was a controversial Professor of Human Ecology at University of California, Santa Barbara who focused repeatedly on the issue of human overpopulation. A member of the Hemlock Society believing in the right of individuals to take their own lives, he committed suicide in 2003.