[dvboy]

Ridiculous the men's doubles is now only best of three, but even more bonkers not to get the Ladies Doubles done tonight too.

In the past the mixed doubles final would be the last match of the tournament but that's been moved to Thursday night.
One reason for having the ladies' doubles on a different day to the singles is in case there is a player involved in both. They have committed to certain parts of the schedule for broadcasters.

I imagine they would have wanted some flexibility in today's schedule to move juniors or wheelchair finals onto the two big courts should the weather have been worse. Court 12, which has big stands round one side wasn't used today because of high winds otherwise some of the juniors matches would have been played there today.
However they haven't needed to change anything, and there are plenty of mixed invitational doubles to keep those who want to stay at Wimbledon entertained.