"Nobody's stopping you using Bing, etc., either."
But Microsoft was fined when it abused its dominance of desktop operating systems to promote its browser, or media player, and was fined also when it attempted to hinder interoperability with its server OS when they was much more dominant than today,
That despite the fact people could have installed and used a different OS, browser, or media player easily if they wanted, just like you can use Bing today - much more easily, for example, than you are allowed on Android today, for example.
Still, it doesn't matter who you achieve a dominant position (as long as it it not illegal), if your are better, cheaper, free, more beautiful, or whatever, and how many fanboys you may have.
Once you did it, your bound to stricter rules, regardless of your name or logo.
Why shouldn't Google be fined today for the same very reasons? Google is the new Microsoft. And because of the data it slurps, even more dangerous (and that's why MS is trying to fill the gap going full slurp mode as well).
Thanks to heaven this side of the Atlantic is not yet all sold to some BigCorp whims... although not a few looks to be ready to sell their souls in exchange of a few free GBs somewhere and a little code.. very cheap, for Google.