The purpose of status matching is to encourage someone to change loyalty to another airline, or at least to remove a barrier to changing. In other words, you do it to help one of your competition's best customers ditch them.

Matching status within an alliance would be perceived as an unfriendly act, "poaching," sort of like trying to date your roommate's b/gf. There might be a few situations when it could be OK, such as (to use a oneWorld example) if someone moved from Australia to Chile and found that LAN Chile now made more sense as a home airline than Qantas, but they're rare and would probably call for special treatment.