The FTC did investigate Google for this exact same thing, and the investigators recommended action be taken.

http://graphics.wsj.com/google-ftc-report/

"Staff concludes that Google's conduct has resulted - and will result - in real harm to consumers and to innovation in the online search and advertising markets. Google has strengthened its monopolies over search and search advertising through anticompetitive means..."

It went nowhere though:

"The staff recommended bringing a lawsuit challenging certain Google practices. The Commission ultimately voted, 5-0, not to bring charges against Google."

According to official logs, Google lobbyists were at the Obama White House more than once a week on average. Donations to Democrats over Republicans was something like a 95-5 ratio from Google staff. Multiple former and future Google employees were top election campaign staff. That kind of near-perfect integration between the world's most powerful information corporation and the world's most powerful government was never going to be undermined by something as nebulous as "monopolistic business practices."

The US antitrust regulation that led Google's acquisition of DoubleClick and Facebook's acquisition of WhatsApp happen? That one?

It's really simple: Corruption. The former FTC Commissioner, Joshua Wright, was actually paid to fabricate academic studies claiming Google wasn't a monopoly, which Google then used as 'independent' expert testimony. Google's funded about half of Congress in some way or another. Dozens of Googlers held high-ranking positions in the Obama Administration's White House. (Including many relating to tech, such as the head of the Patent and Trademark Office, the White House's CTO, etc.)

Google has invested significant money, resources, and manpower in the United States government, and at least, during the Obama administration, was perceived as an ally to the general agenda. We have yet to see how much changes under Trump, the rumor is Joshua Wright is already back involved with the FTC, but the Trump administration has lagged on actually getting all these agencies re-staffed, and who knows what'll actually happen: https://theintercept.com/2016/11/15/google-gets-a-seat-on-th...