While it is not common on Bandcamp, some releases need to be purchased to be able to stream them, this option is not available for bandcamp links.

There is only "stream for free".

Example: https://circum-disc.bandcamp.com/album/the-book-of-pig

You can listen to excerpts for free, but only after purchase, you will be able to listen to the complete tracks (streaming or download)

This is just an example, I came across a more examples where 1 or 2 tracks were enabled for free, only after purchase, one is possible to play the other tracks. (it would require some time to dig up these examples, but if needed, I can post some more as I come across them over time, let me know in that case.)