It eliminates one way of forging results. Without stating the seed, people could consistently fail to reproduce your results and you could always have "oops, guess I had a bad seed" as an excuse.

Why does this matter? If people consistently fail to get results similar to yours by using different seeds, your results are invalid whether or not you made them up. And if people consistently do get results similar to yours with different seeds, your results are valid whether or not you made them up. No?

Even in your counterexample, the random seeds being reproducible and published is still important.

you can investigate the proportion of "bad" seeds and suss out the error bounds of the simulation

How does publishing seeds help with that? You do that by examining different seeds. If you know what seeds were used in the paper, this process doesn't change in any way.