Not can't-can't, but realistically they can't. Per TFA:

> Microsoft CEO Satya Nadella testified that Google's claim that search users have choice is "bogus," while confirming that efforts to compete for default status for Bing failed, despite Microsoft being willing to take billions in losses. At one point, Microsoft even offered to sell Bing to Apple, but Apple rejected that deal, allegedly because the deal it had with Google was just too good to let go.