I'm not going to attend my friends wedding
Why wouldn't you attend your friend's wedding if invited?
Several reasons. It's a wedding, he's probably going to say things I don't want to hear and I'm going to spend a lot of money on a little bit less fun for a short time
The reasons for not attending are valid but you should let him know as soon as possible. There are a lot of expenses in a wedding and it would help him to know that you are not coming so he gets an accurate head count.
I didnt want to go to the wedding anymore so it doesn't matter if I tell him or not. They are doing it for themselves, not for me. They are always bothering me. I don't have a reason for not going to the wedding anymore. Everyone is happy.
Of course it matters. They'll be wasting money to pay and feed you even if you're not there. It's their special day and they have a right to do something for themselves and not you.