MIL only offers to baby sit when their Dad is home (short description)

My husband and I have 2 kids, a 2yo boy and a 5mo girl, who are easygoing and well-mannered. The only close family we have is my MIL who lives a block away. She has only offered to look after our kids once, and she said she would only do it while my husband is home, which just seems really odd to me since I look after them by myself while he works out of town for weeks at a time. Is that odd or am I odd for expecting grandparents to want to be more involved with their grandkids?