It's not about belief really, it's about necessity. At google it basically rains ad money 24/7, that plus backbone internet traffic is where the vast majority of their money comes from, and it's a ton of money. For everything else it doesn't matter if it's successful as a business or not. In fact, the best case scenario is mediocrity and barely breaking even in terms of costs. Because that means there are no consequences, no bigger implications, no expectations for improvement, etc. Google is sitting on several enormous multi-billion dollar businesses (youtube and office tools, for example) but they don't care to actually develop them into such. Right now they can afford to not care, and all of the internal incentives are aligned to promote not caring.

I agree with you. The only downside of this attitude might be the customer trust on the long run and with their future products. Basically, how long can they afford to be mediocre in those areas and will they eventually run out of people who weren't burnt for their money?

Also upcoming public awareness about ads/tracking and how to block them might bring significant changes in their revenue success.

Ads in general are in a long, slow slide into oblivion, so google will likely eventually have to change, but when the crunch comes will they be able to?