Actually, standards are near
Symantec uses a SCSI command extension known as WRITE_SAME with an UNMAP flag, which T10 has (or will soon) ratify. T10 has also defined the UNMAP command which affords a bit more cooperation between initiator and target, this too is ratified (or will be soon).
Most of the industry waited until the two standards stabilized before implementing, and we should soon start seeing more file systems, volume managers and hypervisors using one or both of these APIs.
FWIW, these APIs have value far beyond just freeing up space in thin devices - Symmetrix will support these APIs for non-thin devices as well, interpreting them to mean that the UNMAPped blocks need no longer be replicated (for example).
Also, as with the SATA TRIM command, some Flash drives will support these APIs as a means to improve performance by freeing up blocks that are no longer needed...