Desperation and hunger for control. The streaming model - as well as digital stores - are based on controlling media; companies can dictate what products are sold, when, to who. At any point they can pull them away effortlessly, edit, raise or lower prices. The ongoing war against piracy begins first as a war against physical media and any kind of independence the customer might have when picking their products.
Now, aside from that control, the biggest corporation in the planet have also centralized their offers and distributing systems. The latest wave against anime & manga is most likely caused by the buyout of both Crunchyroll and Funimation by Sony, and the other big names in the game have also been solidifying themselves in major buyouts, except the profits aren't coming. They need to justify their expenses, maintain their control, and make an example, so the last isles of independence must be attacked.
This is definitely the quickest I ever rushed to a website to backup my favorites