Car seat bases necessary?

Shannon
I bought a chicco stroller/car seat combo and of course it came with a base. Being a first time mom I'm just wanting to know if the bases are necessary or just a convince thing? Back when my nephew was a baby I remember car seats didn't even come with bases you just strapped a seat belt around them, which my car seat now does have something that says if no base strap here. I plan on using rh3 base in my car I just need to know if It's necessary to buy more for my husband and inlaws.