Why is it important that an actor works with: -Energy?

It's important for an actor/actress to have a lot of energy, so they capture the audience's attention and keeps their attention until the end of the show.
Also, when they have a lot of energy it shows that they're prepared to do whatever's put in front of them.
It also shows that they're enthusiasm.

-Focus?

It's ridiculously important that actors are always focussed.
They need to be focussed so that they can learn their lines quicker, so they don't distract the other actors around them.
Also, when an actor/actress or a group of actors/actresses focus, the outcome is much greater and they guaranteed to put on a great show just by shutting up and listening to the Director and the other actors/actresses.

-Complicity?

It's important to have complicity within a group of actors/actresses, because it helps the whole group get focussed quicker, and improves the work you all produce. If a group of actors don't have complicity the it's harder for them to work and concentrate in a group because they'll just be chatting about irrelevant subjects when they should be talking about the work.
Not only that, but when they have complicity within the group, the focus is so much better and it's easier to work with a bunch of focussed actor rather than mucking around actors.

-Trust?

Trust is one of the most important things to have within a bunch of actors because if they don't trust each other then they won't be as willing to put themselves out there because they're be scared of messing up. While if the actors trust each other, they don't need to worry about messing up because they can rely on the other actors to back them up and help them out. They also need to trust that the other actors/actresses don't laugh at them.