Meta Sr. Software Engineer interview questions

I had a phone interview with a Facebook recruiter. That lead to a phone screen with an engineer and code tests using a shared text editor. I was then invited on-site for an all day marathon of four 45 minute whiteboard interviews. The on-site was odd. Of the 4, 2 interviews were decent and work related: high level discussions of design. The other 2 were standard Valley algorithm tests. I really don't see the point of these things. They have no relation to actual work and are completely arbitrary.