Here is your list of explanations, at least for why they have to look so serious in coffee shops... 1) their vision is declining so they may furrow their brow t

Here is your list of explanations, at least for why they have to look so serious in coffee shops... 1) their vision is declining so they may furrow their brow to improve their vision when making eye contact, 2) they know not to trust people that smile all of the time, 3) they have other people, typically their children, to worry about, 4) and 5) they are more likely to have been up for several hours and had their expectations of the day's schedule changed before arriving at said coffee shop, and 6) they don't want to be seen as flirting with a younger person and potentially invite public ridicule