RMAN blockrecover uses full backups only

Hi!

I read in the fine Database Backup and Recovery Advanced User's Guide (10.2.0.1), that
for using the BLOCKRECOVER feature...

"You must have a full RMAN backup. Incremental backups are not used by block media recovery."

I would like to know if this restriction is caused by the existence of a theoretical or a practical obstacle.

Any comments are welcome.

-- 
Baláz Lécz
System Engineer, Hungary