WalveMalve ~ I beg to differ on two things.
If you are cast from an open call you can still negotiate your contract.
The same costumes are not used over and over again. Equity states that each performer must have a new costume.
Most of all, I think it sticks around because of it's message and how that message is told.
"For me, THEATRE is an anticipation, an artistic rush, an emotional banquet, a jubilant appreciation, and an exit hopeful of clearer thought and better worlds."
~ an anonymous traveler with Robert Burns