Why did Michael tell Julianne, his best friend, about his wedding on such a short notice?

In My Best Friend's Wedding, the main character, Julianne Potter (played by Julia Roberts) is told by her best friend, Michael, that he is getting married in 4 days.

This doesn't make sense to my wife and me since they are supposed to be best friends. Who tells their best friend about getting married on such a short notice?

I mean, you usually send wedding invitations weeks in advance, so people that are supposedly much less close to Michael must have known about the wedding long before Julianne, his "best friend".

Your "best friend" should be one of the first people to hear about you getting married.

I know that the USA is a large country, and they probably live far from each other at the time before the wedding (I don't remember where they live), and they had fewer means of instant communications 20 years ago (mobile phones were less common, and there were no Facebook, Whatsapp, etc...), but they had landline phones, as well as emails.

Is it explained anywhere in the film? Or was it explained somewhere off-screen (perhaps in some interview with the director or actors)?