If airlines were that concerned about security issues they would have requested that crew hand each and every piece of the uniform back in and account for it.
Recently I went to a large office building in the centre of Sydney and what should I see in the lift but a very professional looking business man thank to the old Qantas jacket he was wearing. The Qantas gold buttons with Kangaroo sticking out a mile, proud as punch he was.
Old uniforms can even be purchased on e-bay these days.