Sounds like you're wasting a lot of people's time and resources.
One possible angle - perhaps openly publishing payroll info (name, title, pay) should be a requirement for all companies that receive an H1B or other work visa.
Keep in mind, there is precedent. Information about how much a house sold for is public. Imagine if, when you were selling your house, you only had a bit of information gleaned from conversations with neighbors here and there, whereas the buyer had a massive database at his or her disposal with exact prices for every house sold in your neighborhood in the last 50 years. You'd be at a massive disadvantage. That's the situation employees are in.
I had a friend who worked in a job doing social research, and one of the jobs was talking to people about childhood sexual abuse that they had, a job that was only done by the more experienced staff. This is random cold-calling to strangers, and it was handled very delicately, reminding the person at regular intervals that they can stop the survey any time and that all questions were optional. He said the odd thing was that if someone started the survey, they generally completed the 20-minute interview, and it was only in the demographics section at the end that people bridled a little - at the 'salary range' question.
Some people don't care about who makes what salary. A lot of people use it to varying degrees as a social status signaller. I've tried being open about mine, and these days, I'd prefer not to share, though I still do with close friends who I know aren't wanky about salary.
This is really a consequence of a culture that confuses material compensation with personal worth and success. I wonder if this is different outside of the western/North American job market.
It's a market, if you find people are consistently wasting your time, you probably just don't have anything good to offer.
If you think they deserve to have their time wasted because their interview processes are inefficient... well, I guess I'll just say that I disagree with you strongly.
One perk of my current gig is a very high level of flexibility (I'm in the actual office maybe 15-20 hours per week, and work from home or coffeeshops the rest of the time), which makes this much more viable.
Really? I find they are either an hour in the office or a few 30 minute phone calls. At least in tech. I know in other fields they have all day group interviews with lots of team building stuff but I haven't encountered that in tech (well at least with startups).