If you have 10k jobs and 500k applications, that's 50 applications per job. Spending a few minutes on each application would mean a few hours for the initial screening for each job, but if that job is filled, you'll get a person who'll stay there for a few years. How is that not worth it? Why would you need to automate it? If you're interviewing for people to do some quick task and leave, sure, but companies want long-term hires.