I get that they need to cut a large amount of people before live interviews
You've just answered your own question. Leetcode is meant to be a filter, nothing more.
but hackerrank/code signal have the ability to test
I'm not familiar with those things, but I don't think companies using things like leetcode actually care how good they are at skills/knowledge testing. I think they just want a coarse filter that doesn't depend on a human making initial assessments. Leetcode does that.
And it works! For instance, I can't imagine being willing to engage in a leetcode test to get a job, so I am automatically filtered out of some positions without them doing a thing.
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You've just answered your own question. Leetcode is meant to be a filter, nothing more.
I'm not familiar with those things, but I don't think companies using things like leetcode actually care how good they are at skills/knowledge testing. I think they just want a coarse filter that doesn't depend on a human making initial assessments. Leetcode does that.
And it works! For instance, I can't imagine being willing to engage in a leetcode test to get a job, so I am automatically filtered out of some positions without them doing a thing.
What about during live interviews though? Not sure if I see the justification for DSA interviews there anymore
I've never been given anything like a leetcode test during live interviews, so I didn't know that was a thing.
I'd take it as the interviewers being lazy and perhaps a sign that they think there's a technical solution to every human problem.