If someone buys my music on iTunes, Amazon, or in a record store (remember those?), let alone streams it on Spotify, it’s all short-term money. That might be the last interaction I have with that particular fan. But if I give that fan the same record for free in exchange for a connection (an e-mail and a zip code), I can make that same money, if not double or triple that amount, over time. And “over time” is key, since the ultimate career success is sustainability.
An album is a one time purchase where the artist makes almost no money. Artists make money from concerts and merchandise. The incentive in that case is to expose themselves to as many people as possible.
The only people scared of free music are record companies.