Sure - but as you can see here the focus on "ditching spotify" is often ethical. You can absolutely use services that have an artist pay-rate of $0 per stream, but I don't think people typically advocate for that - and indeed this author does not seem to either (otherwise they would have no collection size issues).
They will likely get the most money from the T-shirt because the percentage that the artist gets is much higher than any percentage they get from the distributors they distribute through (in case of both Spotify and digital albums they are likely to be the same distributor: Warner Music, Sony, Universal or some such)
I expect many people think: "fuck spotify" and "i dont think piracy is bad" at the same time. I don't think leaving spotify on an ethical basis implies any specific opinion on piracy.