Having been an interviewer at a FAANG for many years, I can explain
some of the logic behind it. I'm not saying this logic is
valid, but it's how we got here, imho.
First: we no longer trust the hiring manager alone, because probably they aren't a strong developer. We instead trust strong developers that are well trained at evaluating good devs. At the same time, we don't want to thrust a dev onto a hiring manager, so they also need to interview you too and have a say.
Second: Is it really fair to have just one or two developers evaluate you? When I first was an interviewer, I liked everybody! I would have hired them all. So getting multiple data points matters. Best to have at least a couple dev interviews.
Then there's the whole problem of needing to evaluate you on multiple dimensions. Can one interview really tell if you're good problem solving, coding, algorithms/data structures, and any specialization the role has? What about the soft skills aspect? We're going to need to have at least 3 or 4 interviews to cover all these aspects. These roles pay a huge sum of money, so there's a lot of worry that someone will be hired who doesn't really meet the bar, you know?
But now we have a bigger problem: if we're going to invest 4+ people to spend an hour of time with you each, we'd better have some data points that you're worth that investment. So maybe we need one or two initial interviews ahead of time to weed out any obviously unlikely candidates.
After that, it's every other company going "Oh shit, Amazon does 6 interviews? We should do that too!".
First: we no longer trust the hiring manager alone, because probably they aren't a strong developer. We instead trust strong developers that are well trained at evaluating good devs. At the same time, we don't want to thrust a dev onto a hiring manager, so they also need to interview you too and have a say.
Second: Is it really fair to have just one or two developers evaluate you? When I first was an interviewer, I liked everybody! I would have hired them all. So getting multiple data points matters. Best to have at least a couple dev interviews.
Then there's the whole problem of needing to evaluate you on multiple dimensions. Can one interview really tell if you're good problem solving, coding, algorithms/data structures, and any specialization the role has? What about the soft skills aspect? We're going to need to have at least 3 or 4 interviews to cover all these aspects. These roles pay a huge sum of money, so there's a lot of worry that someone will be hired who doesn't really meet the bar, you know?
But now we have a bigger problem: if we're going to invest 4+ people to spend an hour of time with you each, we'd better have some data points that you're worth that investment. So maybe we need one or two initial interviews ahead of time to weed out any obviously unlikely candidates.
After that, it's every other company going "Oh shit, Amazon does 6 interviews? We should do that too!".