The value is similar to that of internships - the amortized cost of a 6 month 'trial period' should be similar if not cheaper than false positives that are a lot tougher to fire so you avoid dumpster fires like Amazon's mandatory attrition rate. I also wouldn't call it giving up there lives, when they know what they're signing up for and are presumably getting paid a similar amount to the the full time role they're applying for. Now if FAANG companies try to use their reputation to get cheap labor with no intention of hiring I don't have answers to that, but I can't imagine it would be worth the cost.