Nobody protests when modeling agencies seek the young and attractive because it is part of the job.
The problem comes from each person's interpretation of what the jobs is about from the job title, and the employers' discretion in advertising what the job requirements are. They aren't going to say they want someone that looks cute because they like to look at cute girls, or that they want someone who at least potentially will provide sexual favors.
As an owner of companies, I protest that I cannot hire based on MY criteria. It's my company, and I'll run it the way I want to, as I am the one that will win or lose based on my practices.
I go further. I think discrimination should be allowed, period. All types.
Robert is correct. Being up front about what they are looking for prevents wasting everybodys time.
An employer is going to select as he pleases regardless of what the laws say. For those over the hill in employability, that's life. If you don't like it, start your own company. Then you can make the rules and live or die by the consequences of your decisions.
You CANNOT force wisdom or decency down peoples' throats through regulation.
If an advertisement says they want a young and attractive female, there is a reason. Obviously there is some feature that the employer feels can only be done by such. Maybe it is visual, maybe sexual, maybe financial, whatever. If you are older and think you can do the job, and can/will provide tje features the employer wants, it's up to you to convince.
It is sad but true, so accept it and do what you can. If you are a 40 year old applying for a job where the employer wants a pretty young thing, maybe you need to add that you have excellent oral sex technique, or a cute young daughter that will be willing to "help out" when needed. Oh, you say what? Yes, its rude and disgusting. Much of life is. Accept it, don't apply, and get over it.
Maybe it isn't visual or sexual. Maybe it's attitude, ability to mold, pay expectations, longevitiy, who knows. Don't expect the employer to tell you which. You always have the option of making a list of all possible reasons and adress each, explaining why this doesn't apply to you during the interview.
If it were me, I'd go as far as to lie and then say I did what I had to do to get this interview, just like I'll do what it takes to fulfill the commitments of this job should I get it.
The employer wants what they want and no complaint or regulation is going to change that.
For example, you want to be young and pretty. Can any regulation change what you want?