I headcanon that since Kurt and Rachel are both athletic and competitive people, they tend to wear each other out with very physical casual “dates”.
After a morning that starts with some yoga and a jog in Central Park, moves on to a fencing lesson, takes a breather in the Danger Room for some space-pirate booty stabbing, and ends with a round of four square or twelve with some of the students, they take an impromptu nap to a movie that they were totally planning on watching. (and this happens a lot.They just nap places.)
I think their relationship is very low-key aside from the fact that they spend a lot more time together. Maybe Rachel isn’t fond of PDA and Kurt wanted to take it slow.