No, definitely not. A lot of freshmen especially prefer to just have the time at home. Others get UROPS or internships somewhere else or travel to other countries, etc. My son opted to go to IAP and just relax and have fun - took a boot camp class and a Scuba class and just enjoyed being with his friends without the stresses of school.
Personally, I don't think I ever did anything "official" for IAP, other than take phys ed classes that I couldn't fit into my schedule during the semester. I mostly just worked at my UROP during the day and had fun with my friends in the evening.
There are a few freshman courses (8.01L and 18.02A) that keep going into IAP, and there are a couple of departments that have a required course (for upperclassmen) held during IAP. For the most part, people just do what they want and have fun. There's no additional charge for staying in the dorms during IAP.
Thanks for the replies. Dh and I are celebrating our 25th anniversary and were hoping to have the family together for a special event, but it's right at the beginning of IAP. Of course our son will decide whether or not to do it, but I didn't know if it was mandatory. It's sounds great, for sure.
Do keep in mind though that while staying in the dorms is free, the dining plan does not cover that time. So they either have to pay for an additional plan (expensive and only at Maseeh) or cook on their own. My non-culinary-talented son lived the month on poptarts and ramen - guess it was kind of a "real" college experience!
IAP's not mandatory, but there are a lot of optional courses and seminars that you can take for fun or for credit. However, I know that 8.01L (an extended version of 8.01) goes into the IAP, but I know I won't be taking that.