If I have more than enough memory, can it still be beneficial to use compressed textures?
Because memory bandwidth is not free.

No matter how much RAM you have, it takes less time to read 1024 bytes than it does to read 1024 KB. Compressed textures, relative to 32-bpp, can offer compression ratios of 4:1 or better. That's at least one quarter of the memory bandwidth costs of fetching the texture.

If your rendering uses lots of textures, reducing bandwidth pressure can improve performance.

Alternatively, the more memory you have available, the more memory you can use. If you consider 1GB to be "plenty of memory", then using compressed textures allows you to store the equivalent of maybe 2-3GB worth of textures. So now your textures can be larger, more detailed, or more varied, all within the same "plenty of memory" space. Or you can use some of that reclaimed storage for more meshes.

There's never enough memory; there's only a question of how much you're willing/able to use.