I got my first serger 25 years ago. I love my serger. That being said, I have never used my serger for quilting. I sew a lot of clothing for myself, my kids and my grandkids and would not consider sewing garments without a serger. I have also used my serger for many home dec. projects like curtains, tablecloths, napkins etc.
About the only time I use my serger for anything quilting related would be to finish the raw ends of fabrics if I decide to prewash them.
I guess to answer the question of whether you need one or not would depend on what kind of sewing you do.