We are happy connected to friends and family. Being alone (or eating alone) is ok in itself, but it may also be a single that the person is being disconnected with the social circle. This TED talk has pretty good points on the negative effects of being alone.

https://www.ted.com/talks/robert_waldinger_what_makes_a_good_life_lessons_from_the_longest_study_on_happiness?language=en