Do you have to show up for the court date if you weren't served summons?

Yes! Otherwise you can be held in contempt of court and fined or even jailed. Don't ignore the legal system.

Added Answer:

No you do not have to appear in court on a civil court summons if you do not want to and you will not be held in contempt, fined or jailed for doing so. The only adverse consequence that will result in ignoring it is that the court might grant the complaining party a judgment against you for whatever it is he is asking for in the complaint.

On the other hand, ignoring a summons in a criminal action or a subpoena can result in you being held in contempt, fined or even jailed.