Roundedness has a number of cultural meaning for the chinese. Firstly, it can symbolize "reunion" as exhibited by the chinese word "tuanyuan 团圆" (literally 'united and rounded'). Secondly, it can symbolize "success" as exhibited by the chinese word "Yuanman 圆满" (literally "Rounded and Complete"). As unity and success are somehow tied to 'roundedness', it's not surprising that chinese eating tables are also rounded in shape to symbolize such meaning in chinese eating culture, esp. in social/friends/family gatherings.