I'm a "top-tier" candidate (at least, tech companies offer me a lot of money to work for them) and I don't think I'm alone in not really caring much about the process, as long as it's sufficiently technical that I'm not worried about working with people who can't program. If the full time job at the other end is interesting enough, the 6 hours of whiteboard/takehome/code review is just an annoying cost of doing business.

And, if we're being really honest here, there's a ton of informal backchannel talking that goes on, so your interview "performance" regardless of medium is affected by that at many places. I think if you aren't actively working to make your interview process objective, it's being strongly affected by many biases and informal relationships.

That's all to say that on the balance, taking up "some" or "all" of a candidates time isn't that interesting of thing to think about because the process is so broken in so many other ways and this one doesn't have a huge impact.

Adding to what the other person said, I've leveraged interviews to get flights to cool places. A free day trip to Seattle, nyc, or sf is a nice perk, and in my experience companies are flexible on travel arrangements (eg. Can you put the return flight a few days later, I'll handle any extra hotel costs).

I can't get that from a take home assignment.