Because they only want to socialize with people who ware a pair of socks two times and
.
Give them to Goodwill
.
A place the poor can buy the stuff they walk on and discard what they don't like
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Because you are there at an age where you start thinking about settling down, plus grad demands are strenous and so you develop a strong friend/relationship base.
Probably the same reason many couples, regardless of occupation, meet in college. Or many couples meet at their place of employment. Close proximity and shared interests.