As a fellow actor, I must disagree with your representation. That isn't entirely accurate. Certainly if you are doing a general audition for a theatre company that is true, and often they will give you a script the day of as well. But if you are auditioning for television/film you have to memorise "sides" (scripts) that are unique to that project. Depending on the size of the role, that can be quite a lot of pages. I had to memorise 8 pages once and I had a week to do it because of the length. Only for commercials is there usually just the day before or day of. Then often actors hire acting coaches to help them with their sides, to make sure they are giving a truly quality performance. Then you have to make yourself look the part, so do your hair, your makeup, get dressed up. Depending where the audition is you might have a long distance to travel, sometimes you have to take a taxi if the location isn't near public transit, you might have to get time off from work to do it etc. So not only are you preparing for something that you will never need to use again, you are also spending money. I suppose you could argue it's still not comparable to the amount of time writing or illustrating takes, but I don't think that's fair. As an author I have never felt it took more work to write something for a written audition than for an acting audition. It's just different work.
So you could say it is wasted time and money auditioning like such. BUT. If you are a clever actor you realise that none of it is actually wasted. Yes you need to, as the saying goes, "spend money to make money", but more than that doing a good audition for a casting director or director herself can mean future auditions down the road. JUST LIKE illustrating for a publisher who rejects the work now might result in them requesting you down the road. Further you know that write for hire I wrote about auditioning for? Yesterday they asked if I'd be interested in trying for a different project. Now I have no time right now to do it, but they remembered me, my name came up in conversation. It wasn't just that they rejected me and it was a waste of time. It actually was more like an investment.
Another example, I recently was a reader for a casting director. This means I stay all afternoon and read opposite people who are auditioning for him. It's unpaid. It's a long day. But I did it. Why? Because a) I wanted to see the world from the other side of the camera, b) I wanted to show my acting chops to the casting director. And guess what? A week later he brought me in to audition for that same project. The investment paid off. It doesn't always. That's a risk we take. But that's kind of life in general.
Being in the arts is hard. We do a lot of work for many times little reward, and no it isn't fair. But that's what it is. Expecting some kind of straightforward, "I audition and get the job" kind of situation is not reasonable (and is a little selfish, you aren't the only one auditioning for things, if the idea is that you get this special treatment that if you put in the effort than you deserve the job, that means all the other people putting in the effort for the same job get a lesser treatment). So you can bemoan the fact that you should not have been rejected after you put all that time into it, or you can realise this is the game and decide if you want to play it or not.
Certainly as Myrealana said if they took your work and used it that would be taking advantage of you and that is wrong. But you knew you were auditioning. You knew it wasn't a sure thing. You decided to do it. That's what a lot of us do. If you want to see every effort you put in that doesn't succeed right away as a waste of your time, go for it. But remember, this isn't a short quick bank robbery. This is the long con. And there are others out there who get that.