People upvote the content they want to see. Implicitly, whether something is paywalled or not is already included in that judgment. What's more, people keep upvoting paywalled content because non-paywalled content isn't providing the same level of content. By not tolerating paywalled content you are making an explicit call for less content of the type that HN readers say they want to see.
You could make the argument that HN readers shouldn't upvote the things they are upvoting, that HN would be a better place if people didn't upvote the things they are upvoting, or that there might be a longer term benefit to be gained from accepting short term losses by eschewing paywalled articles. Those are all things people could argue.
But the fact that they show up on the front page with regular basis is explicit evidence that, even if you feel they have no value, other people do.