Screeners / Screenout

Why can't you just invite me to studies that I will qualify for, or at least tell me in the invitation what is needed to qualify?
Why am I asked the same screening questions over and over?
Will I be paid for my time despite screening out?
What kind of questions will I be asked in the screening process, and how long will it take?
When I screen out, what happens to my data?
What is a ‘Screener’, and what is the purpose of screening questions?