[kvdveer]

No compression. In the olden days, storage was scarce. While you could compres the bitset, the worst case compression of that bitset would be larger than the uncompressed size. You likely have no way to guarantee the worst case is impossible, so you'd have to reserve extra space. In the end you'd store more data, in a slower to use format.

These days storage bandwidth is the main limiter, so now compression makes sense. When storage size is the main limiter, compression is ironically not very helpful.