In my bizarro completely unscientific visualization it makes sense. Say you have a waterbed made out of very stretchy material. It's bound by a hard frame, but

In my bizarro completely unscientific visualization it makes sense. Say you have a waterbed made out of very stretchy material. It's bound by a hard frame, but the sides of the frame can slowly expand if enough pressure is applied. Without anyone on the bed, the system is in steady-state. The sides can just barely hold the waterbed bladder without expanding. Now let's say a bunch of kids jump onto the waterbed. They make indentations in the surface which cause them to roll towards each other (gravity) but also the waterbed is trying to repel them (dark energy). The extra force of the kids put on the waterbed's surface causes the sides of the waterbed to slowly expand. As the waterbed expands, the repellent force lessens and the expansion slows until it hits steady-state again (or the kids get bored and go outside to play). Since the universe has no hard edge, it could be there is no steady-state, but the repellent force causing it to expand just gets weaker and weaker over time as matter gets more and more diluted. I guess all this hinges on whether it's matter causing the repellent force, or if it just exists outside of matter.