Makes sense if one considers how many 13” Macbooks and original MacBook Airs were likely being toted around the Google campus in the late 2000s, with Macs being the predominant development platform there at the time.

Further down the road in 2011, Chromebooks appeared, most of which are on the smaller side which also acts as incentive to keep Chrome usable on smaller screens.

Desktop Safari and MS Edge are also decent in this regard, likely a result of their parent companies being makers of popular small-screen computers.