I don't get why people care what others do. I think mostly it all comes out in the wash.
A) In our house, we give lots of presents at Christmas, but then Birthdays are about the celebration (will pay for a fairly expensive party, but the DC will be lucky if I spend £50 on their presents). And if they want anything else the rest of the year, they have to save their pocket money for it.
B) I have other friends who don't spend that much at Christmas but spend loads on their childrens birthdays.
C) I know other people who don't spend much on either, but buy lots for the children all year round. One such mum never goes to town (weekly) without bringing back a little something (item of clothing, toy, book, magazine etc) for her DC.
Of all the friends who do these different things, you cannot point to the child and say those in A) have more presents than C or vice versa. In fact if you look at the stuff the children own it's all pretty much the same, whether they get their presents at Christmas, on their birthday or throughout the year.
And no one method is better than the others. You could argue that it's better not to give at Christmas to avoid the over commercialisation of the event, but equally you could argue that the materialism of the other 364 days of the year has more of a stranglehold on society. It's pointless sneering about extravagant Christmas gifts if your child gets the same amount of stuff but they are simply distributed differently.
I also find that those that give more at Christmas tend to give more practical things too. Myself included. My DC get new underwear, pjs and so on at Christmas. Again, that's no more than any other child, just being given it at a different time. So it's all swings and roundabouts I think. I prefer the live and let live approach without the judging. Not nice and not necessary.