Google hammers any normal site that gets caught presenting a fundamentally different experience to the user than they do the spider. Google is not unaware that Quora, Pinterest and LinkedIn present different experiences to the bot vs the user, they knowingly allow it for giant services. That's the hypocrisy and double standard.
No, it's not to simply sell ads. You build something slick and shiny, then you pump VC money into it and you keep hyping (otherwise known as "pumping") until you can get numbers that look good. You can just spend that sweet, easy VC money to buy users and spend a dollar to make 10 cents because of that "growth" you are buying.
Then, when those numbers you are buying (and also all those fake accounts you are ignoring) start looking really good, you go public, the VCs make out like bandits and all those institutional and private suckers buy those bloated shares, trade places with the VCs and slowly ride the shares back down to zero where they belong.
Zynga IPO: $23. Now around $3
Snap $22 ... ~$16 (LA not SV)
Blue Apron $10 ... ~$2
Box plummeted more than 50% before coming back up closer to the IPO price but has almost never exceeded the IPO price since inception.
And there are a lot more that are newer and still riding the capital injection from the IPO (like twitter).
Wow, really? I figured they're a bit fancier, more serious version of Yahoo Answers. I wouldn't have thought they'd have any venture capital at all.
https://support.google.com/webmasters/answer/35769?hl=en
Quora presents a very different site to Google than it does to the reader ultimately. Google intentionally, knowingly ignores this fact and has for years. They could manually penalize Quora for breaking Google's search quality guidelines in numerous ways and they choose not to.
A user can't freely browse Quora page to page, whereas Google can. Presenting a different site to Google than you do to the user, is about as direct of a violation of their guidelines as you can get.