It's considered an obligation of service to our society/government.. just as we pay taxes, abide by laws, vote, etc. If we want to have access to a jury trial when we're the one being accused or a party in a lawsuit, we need to also be willing to serve on a jury.

Usually, it's not too hard to defer a jury duty summons if there's a legitimate reason, like being out of town, medical issue, lack of childcare, etc.