Evelopedia has this on mineral compression:
Demand for mineral compression has
fallen with the advent of jump bridge
networks, which make it much quicker
and safer for well-established
alliances to move large cargoes long
distances across 0.0 space. However,
it remains a useful option for some
smaller producers operating in less
developed areas, and there is still at
least one active independently-run
compression service.
The focus of most current methods is
on dreadnought-sized ammunition, and
the few remaining modules that have
worthwhile compression ratios and
short build times. Builders of
supercapital ships, however, have been
known to purchase carriers in bulk,
jump them to the build location, and
reprocess them into capital ship
components. Although this is a
time-consuming and expensive process,
it can be outsourced, and it removes
the need for a large number of
dedicated component build slots in the
destination system.
I know of at least one active compression service, so there is still demand for this, even though it may have decreased over the years.