I have an aunt and uncle who did that. Said they were spending their time and money at church. IMO, it was very lame. In fact, it came off a little condescending...like they were doing charity work and the rest of us were wasting time and money on cards. I still give time and money to charity and remember my friends and family with the small sacrifice of some time and a few stamps. (If you want to save $ on cards just write a letter.)
I don't even bother opening the e-cards I get.
I signed, wrote short notes in about half and addressed 60 cards in about two hours while watching the news and having Saturday coffee. I still need to write up my generic this is what happened this year letter and put on stamps. It isn't that much work and it is the only time I get to contact many of these people or hear from them.
Just below e-cards on my list are the cards that are printed by machine on the inside, a computer label on the envelope and a printed return address label. Wow, why bother? I do feel a little obligated to send them, too, but I always feel good that I did.

Especially when MY mailbox is full with cards my family and friends took the time and effort to send to me.