How does Photoshop open RAW files if they’re proprietary?
Adobe has to buy each camera as it comes out in order to reverse-engineer the ability to open these files. Crazy I know, you’d think they could share the RAW format as open-source, but alas.
That said, Adobe does have an open-source RAW file format called DNG (short for digital negative), and using the DNG converter (which is free) you can convert your proprietary RAW files over to an open-source format.
Because RAW files from your camera are proprietary
It’s best to convert them to Adobe DNG as part of your workflow. This gives you a backup and also stores an open-source version that is less likely to be unsupported in the future.
Is it worth shooting RAW? It sounds like a PITA
It really depends on what you plan to use the images for. If you’re shooting images for a coffee table book or images that you want to push further in post-production, then yes. However, if you’re on vacation and taking family pictures at the beach? High-res jpegs are a great option. Photography is full of compromise and it’s a matter of figuring out what the up-side / down-side is for your particular application.