Streaming and hosting white noise on their servers costs them money, most people who are using these podcasts probably just do it while they’re asleep and happen to have a spotify subscription. These people aren’t going to cancel a subscription because they need another app for white noise.

Spotify could add a generator for white noise soundscapes to their app, but there are countless applications that do this already for free, including open source options. If they aren’t giving money to people uploading soundscapes, they can take more money from monthly subscriptions themselves and give more to artists, increasing their profits and making their platform more desirable than their competitors, which has been an issue for them in the past with criticism from major artists and indies alike.

Overall these noise streams exist to game the system by getting people to play for a long time on content that’s probably just made by hitting the play button on a generator app written by someone other than the uploader, and it’s likely the only reason it happens is people don’t want to download an additional free app for that task