Lunch, coffee, beers?

With one week left in this job, I find it surprising how many people want to hang out and grab coffee, lunch or a beer before I go. These are people I generally like, but have never spent time with outside of meetings and hallway interactions. Why, suddenly, do we need to spend time together during my precious non-work hours that are spent doing busy and important things?

I'm trying to schedule this "free" time to see people who are my actual friends!