Google doesn't solve simple problems.

Yes, but that doesn't mean you don't need to know how to solve them. If you can't solve simple stuff, you won't be able to solve hard stuff that depends on knowing the simple stuff cold.

  they may have other obligations like family
  and work they probably won't have time to
  practice such a pointless skill.

Yes, that's a possibility. But once again, if you're Google, you're getting 10s of thousands of applications a week. You can afford to set the bar as high as possible. Every Google employee I know regularly works 10+ hour days there, and sometimes does work at home, too. If you have two applicants of similar skill, but one has more free time to devote to your company, it's obvious who you'll prefer.