“Google has over 170,000 employees and ~120,000 contractors” Vintage Silicon Valley move. Your paycheck says you work for a third-party, then you work for them

“Google has over 170,000 employees and ~120,000 contractors” Vintage Silicon Valley move. Your paycheck says you work for a third-party, then you work for them—-they pay the payroll taxes, insurance, etc. Why would anyone question who is the ‘employer’? Meanwhile, you’re hired by, you work for and are give directions by The Company (here, google). Looks like a duck, walks like a duck, it’s a duck. What’s changed in the past 30 years?