It takes ads to bandwidth and server costs for Spotify. The ads on Spotify are worth less than before, because the ads have less reach. That means Spotify will have to play more ads to cover cost, and because the revenue per ad will go down. Maybe your little action has an insignificant effect, but if millions did what you did, it would have a drastic result.

Never mind that doing this will give your favorite artist a few more pennies at the cost of a different artist that didn't get his numbers inflated. You aren't doing some great good to save the planet.