I've been married 26 years, so you can't, blame it on generation.
We have always sent out our cards to everyone, including brothers, sisters, aunts, uncles, cousins, grandparents, parents signed
-Happy Holidays, (some do not celebrate Christmas)
The ______________ Family
It is really annoying when somebody does something one way, as in the fact that you are a "card" person, and then whines and gripes when everyone else does not do it exactly "their" way as if "their way" is the only way acceptable.
Personally, I would find it annoying to get a card from a reltive for every little occasion, even the non-traditional card holidays like Halloween that you said you send cards on, especially if I know the relative is expecting me to reciprocate a certain way. If you are sending all those cards and then griping that you don't get signed cards in return, then you are not sending cards out of love, but out of trying to make the rest of the family feel guilty that they don't do things "your way."
If you don't like the way they send out cards based on the fact that you do things differently, then just stop sending them so many cards. Maybe, out of courtesy, since you don't approve of their card sending ways, they will drop you from the card list.