Rooter, it is great that you are curious about this, this forum is so that we can learn off each other, as I have so much already.
I think there are no artificial divisions in sex between your own pleasure and in giving pleasure to another. Just because I get pleasure out of making a girl come doesn't make her pleasure any less genuine. I'm sure it only makes it more so! There are no artificial motivations at work. Sex is the ultimate mutual activity.(A lot of the time anyway.)
This is probably the only case where the altruism and hedonism you mention is merged so seamlessly that they become exactly the same thing. This is a miracle of reconcilation, and let's let out a great big cheer for that! Think about that, this may be the only example of this in all of humankind's world. (You are right, charity doesn't always qualify for this.)
Any of those things you mentioned eg "prove you are a good lover", and "boost your own self esteem and ego." Well, if that happens, it only happens as a by-product of your own full enjoyment of the sex. They are small sub-sets to the main game.
Looked at from the opposite angle, suppose you thought you were a poor lover because of a lack of knowledge of technique, and your self-esteem subsequently suffered. How would either of those be good for the gir'ls own pleasure? Increase your own pleasure though hers, and then both of you are in front.
This doesn't have to mean she has to come. For example, I'd be very interested in a girl that would take her own pleasure from being handcuffed while she sucks my cock while I whale the tar out of her bare arse with the flat of my hand. (Well, not that hard!) But I also love it when the girls come purely from my deliberate intentions towards them.
I know you are saying that you mean no criticism. I think that now that I have described how and why altruism and hedonism are identical when it come to sex, even that minor criticism, if you have it, you need no longer have.