Why should a clan need a new alt? Alts do not participate in Strategus, it's only for the main characters.
Clans also play on the seige and battle servers. If they're running a build where a shield wall is useful, but you don't have a shielder, then STF would be the optimal way to get a shielder in no time. Then the clan could get more multipliers. If they need archer later and you just delete and go archer, it's eventually going to get to a point where there's a signifcant advantage in having an easy swap fully stat filled character.