Sorry, late to this but the idea that 'sharers' are greedy and selfish just means that some of you have had the misfortune to meet some self absorbed pillock's.
We're sharers, my family are not. So when I wanted a big Chinese meal for my birthday, I was paying, my DF, DM and DSis ordered their own. DH and I ordered a mix that we liked and my 9 year old nephew asked if he could join in - there were dishes he hadn't been allowed to taste before as nobody else were sharers.
Every single time he reached for something that wasn't technically his dish my DF tried to intervene. I spent the whole meal talking to a 9 year old about the food, which flavours he liked best, seafood or meat or the veg etc.
Same DF was horrified when we went to a lovely tapas bar and, when I realized that my rabbit dish had all the inner bits, heart, liver, I shared them with DH because they were the best bits. Teeny, tiny morsels of food that I gave to DH because they tasted amazing.
DF simply doesn't understand that level of sharing, lack of selfishness.
I want to share the good bits with people I love, or even only like. Why is that selfish, or in any way odd?
From my perspective anyone who doesn't want to do the same is odd.
Then again I don't mean share a whole meal, or enforced sharing because I can respect a non sharers choices.