You don't understand what these people do for a living, which is why you typed out this "but in a completely different field, this doesn't work".
True. In your field, it probably doesn't work. But for junior analyst, this is the only way to make it work. The job is to trawl through time sensitive raw data and pre-collated data sets, to generate collated topical data sets for senior analysts. Ingestion of data is constant, creating constant need for junior analysts to trawl through the next data set.
This is a job where working 18-20 hours a day, 7 days a week for years at a time is a norm, and working less than that is an exception that requires high level connections. This job kills people because the tempo is insane, and senior analysts demand quality on top of numbers. And there's always more time sensitive data to trawl through, and where collation is worthless if not downright counterproductive if it isn't done in a timely manner.
This is why older people can't do this job. It's not survivable outside twenties. This is also why this job is exceptionally well paid even for new hires. It takes very exceptional individuals to be able to do this job. You need to be high IQ, educated in complex mathematics and statistical analysis, savvy in relevant software packages and their applications, require no more than 4-5 hours of sleep a day to be fully functional (with stimulants) and be driven to actually want the senior analyst position badly enough to be willing to suffer through years of junior analyst position.
There's a reason why this job pays big.