Between 2004 and 2007, when I designed and implemented ROW_FORMAT=COMPRESSED in the InnoDB Plugin for MySQL 5.1 based on Heikki Tuuri’s rough idea, it might have been a good idea to trade some CPU cycles for I/O bandwidth. Nowadays, with fast solid-state storage being a commodity, it is less so. ROW_FORMAT=COMPRESSED is introducing quite a bit of complexity to the buffer pool and crash recovery. We could make the server much faster if we removed write support.
To allow users to upgrade from old databases, we must retain read support at least for a few major versions.