Asami and Mako aren't that different from real life couples. . .people tend to want to get down and dirty as soon as possible. They want to go out to dinner, be together all the time, and give each other expensive prizes in an effort to prove their worth.
I don't think Asami is evil, but I do think she might be self-conscious, and alone, and needs a man to validate her. As for Mako, he wants an equal to show his affection for, as he is always with his little brother. Asami is someone Mako can enjoy himself with without having to wipe her chin.
So yeah. If LOK wasn't for kids, they'd ******** like rabbits and probably end the relationship rather quickly.