Many of the main roles and speaking parts in major films are cast with actors represented in the union, and usually only actors in the union can audition for that role. If you are not in that union, you are then considered non-union.
Can I wear jeans to an audition?
You don’t need to dress like you’re going in for a corporate interview here. Your clothes shouldn’t be a wrinkled mess, but you also shouldn’t be wearing business attire to an audition. A good pair of jeans can go a long way, and it’s worth investing in a pair for auditions alone.