Why did the Kardashian-Jenner sisters miss Kourtney's wedding?

ok.co.uk:

Kourtney Kardashian and Travis Barker got married on Sunday 15 May in an intimate ceremony. The eldest of the Kardashian sisters, 43, and the Blink-182 drummer, 46, professed their love for each other in the surprise ceremony surrounded by a handful of guests.

Not present at the wedding were any of Kourtney’s sisters or children, though her grandmother Mary Jo 'MJ' Campbell and the musician's father Randy were there.

In pictures obtained by DailyMail, Kourtney was seen wearing a white minidress with a plunging neckline and a heart emblazoned in the middle alongside long fingerless gloves and a white veil.

A source told People magazine: "They had to legally get married first ahead of their big Italian wedding, which is happening very soon. "All the details are set and the whole family, including all the kids, are very excited." Though none of Kourtney’s sisters were present, they were seen on social media and out and about on Sunday.