If someone has invited you to a wedding that requires you to drive for more than an hour, but doesn't think enough of you to invite you to the reception, is it truly mandatory that you go? And since you're not invited to the reception, wouldn't that make it all right to ignore giving a wedding gift?
If I don't want to go to something my conscience makes me believe I should, rationalizing the situation as I did above would guarantee my absenteeism.
"Oh! We so want you to see us get married, and we know it's a 'drive' for you, but we won't detain you with the reception because we are doing a small one with selected friends/relatives. You understand, I'm sure!"
No...no punch, no cake, no mingling? NO GOING.