And the reason is because when you are looking for a job other things are more important than knowing the salary even before you apply or they seriously consider you.
Everyone does whatever they can get away with, and the moment we accept that everything becomes clear. They are all trying to benefit themselves, just as you are by trying to learn some information before the other party feel the need to share it with you.
Having to write a cover letter, customize a resume and sit through multiple interviews just to find out if I can literally afford to work for you is not acceptable and the only reason companies get away with it is because all the other companies do it. This trend needs to die and it needs to die a decade ago.
That's like, your opinion. Millions of people go on job interviews everyday without first knowing the salary offered and in fact in most meetings the salary is the last thing discussed.
What job seekers are begging for is a salary range being included with the job posting. Not doing so just wastes everyone's time when the company low-balls after the 3rd interview and the interviewee walks out the door.
If you want a junior worker for a junior's salary, that's fine, there are plenty of juniors looking to get their foot in the door, but include a junior's salary range so you don't waste everyone's time interviewing someone who's never going to accept your junior offer.
If you want a senior for a junior's salary and think you'll get one by leaving the salary range blank, go pound sand.
No one thinks they are getting away with anything but you. I don't get why you are so mad most people don't consider not knowing the salary beforehand a reason not to go on an interview. Not posting the salary on the job ad has never been the reason a position has been left unfilled.