[photochemsyn]

All the union shops I've heard of have at least a three month probationary period, possibly six, during which you're not part of the union and don't get any special job protections.

Also there are a ton of positions in various fields for which the organization already has someone in mind but still has to advertise the position and do interviews for various legal reasons.

[aaomidi]

There are countries with industry wide unions that provide the same levels of protection by just being part of that union.