I don't believe it is necessary to own a serger, but I could not get along without one.
I always serge my binding edges before sewing onto a quilt.
I also make baby receiving blankets and burp cloths and serge the edges on both.
I was intimidated by the serger when I first bought it, but am gradually learning more and more uses for it.
So all in all, I think it is up to each individual whether or not they need one.
Good luck on whatever you decide.
Sue