If you purchase your subscriptions through Roku, then all your subscriptions are managed in one place (your Roku account) and available to all your Roku devices. This would be primarily for convenience and for people that only watch on their Rokus.
For people that have different Streaming devices or need to watch elsewhere than their home (even though more of these Subscriptions can be watched through the Roku Channel now), then subscribing directly to the Provider is recommended.
Roku Community Streaming Expert Just another Roku user... I am not a Roku employee. Insignia RokuTV, Ultra 4660, Premiere+ 3921, Express 4k+ 3941, Streambar 9102