The streaming services like Spotify are slowly bleeding money. The expenses for licensing exceed the subscription revenue and add revenue for the free tiers. Thus, the Freemium model does not appear to be viable economically for the long run. Apple will not do anything that loses money. Period. Thus, they are using their considerable market power to move the market to something that is sustainable. That is, you pay for the service. Absent this market shift, the streaming players will eventually run out of backers who see a money-losing endeavor. Someone has to pay for all the infrastructure to support millions upon millions of streams. For better or worse, Artist are represented by the labels who demand payment for the rights. Yes, taking away a free tier might drive some back to the pirating of music. If you could somehow economically quantify the notion that someone who listens for free is a net positive for artists, then you might get traction with your argument. As it stands, the folks running these services need to turn a profit eventually. They are not a non-profit charity for emerging artists.
However, with advent of the global Internet, emerging artists have any number of ways getting exposure that wouldn’t involve signing a record deal and having to play with the labels and streaming companies. Maybe you should explore that instead. Asking Spotify, Apple, et al to give away free services is probably not going to amount to much.