I like just having one, and I admit I dont see the problem.
I wouldnt have minded having adopted 2 that I knew would get along,it was my original plan, but when I got there it was just my one girl.
I really would never convince, nor would I want to convince my husband to have to adopt maybe several more rats in hopes that
they would get along when I might just as likely end up with 2 or 3 rats in separate cages we dont have room for and having
to divide my attention to all of them.
Having just one is a perfect fit for our family. I am a stay at home mom,
my kids and I give her attention whenever she is awake. She has a large area for freerange for the majority
of the day. the kids and I play with her throughout the day, she is part of our family.
in the morning & evening she cuddles up on my lap and pet her and she 'grooms' my hands.
She stays up late with my husband and I in the living room and joins us for movies or snuggles with me while I read.
So maybe Im selfish, Id miss this special bond if she were off playing with another rat instead of interacting with me. We love her and she's happy.
She loves us and we're happy.