|I think that is very dependent on family culture. The only family I know in real life who does that is my husband's.
I think it is true that it is dependent on family culture. Neither my own family nor DH's family sends cards let alone remembers birthdays. My sister has five kids and lives in Europe, and my brother has four kids here. DH has a ton of nieces and nephews and they don't exchange cards with us or vice versa.
Instead of keeping up with various birthdays, I prepare the occassional care package (full of little toys and goodies that I find along the way). I keep a box at home and add to it and then when it is full enough, I send the various families a surprise package to let them know that we are thinking of them. DH does this for his nieces and nephews as well. They love it! A package can appear in the middle of the summer or way after the holidays.
OP, I'm sorry that this was so disappointing to you. I have found that early in my marriage and parenthood, I had to sort of build my own traditions if there wasn't something in place. The surprise goodie box worked for us and there is an equitible element to it. Everyone gets recognition and it is fun for all parties involved.