I can't speak to art, but I know with video game piracy research shows that anyone who bothered to pirate was NEVER going to pay for the product. Ever. So the financial impact is minimal at best. Between how much anime I pirated only to later buy and solva64's comment, I suspect it functions more like advertising. You lose almost nothing and potentially gain customers. I'm sure there are reports showing how much digital piracy effects business, but does that show the amount of product taken or the actual impact on sales?
When you release things to the internet, it's only a matter of time before it gets public. Raging about it doesn't help as it'll Streisand things further.
Of course, it doesn't help that his release schedule turned from a week, to a month, and then to several months, without piracy pushing it along.
Artists that do the weekly thing tend to not have people ripping their Patreon as much, if at all. It's the ones that have a month or more wait time that do and for good reason: The ones who faithfully waited get impatient and usually decide to release it for the rest who are also waiting, because they feel they got lied to. But hey, if you said you'd keep to a set schedule, you should be expected to keep to it.
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