I've never found the term life insurance offered through my job to be a particularly good deal - but I'll add that we are youngish, healthy and active. Through the private market I'm getting ~$1,500 per annual dollar of premium. You are getting almost the same ($1,521 per dollar per year). The term through work is just $416/year
I suspect it gets offered so frequently because people are very bad at math, or more to the point don't bother to compare apples-to-apples, and the insurance companies have realized this and exploited it. $3/mo sounds like peanuts and $15k is about what most people owe on their cars, so it seems like a good deal. Only you are smart enough to realize it isn't.