I'm sorry your birthday was a disappointment, Roobi. I'm sure your friend didn't mean to hurt you. She may have had other things going on in her own life that got in the way, but I can understand you feeling upset that she didn't phone you or ping you a message.
More generally though, and not directly connected to the OP, I don't think that the only reason cards are going out of fashion is the cost, as suggested above. The politics of card sending put me off it ages ago. People get upset if someone forgets, expect reciprocal cards (even crossing people off lists if they don't reciprocate) see them as an obligation, assume that if they don't get a card it's because the would-be sender 'couldn't be bothered', threaten not to continue to give presents to children who don't send cards - on and on it goes.
The bad feeling cards can cause makes them a liability, IMO. They are profit-spinners for the manufacturers, bad for the environment and getting a hundred bits of cheap card with mass-produced verses inside does not make someone more loved than if they didn't get any. It's more to do with the expectations and culture of their family and friends.
I know people (eg my mum) who continue to see her worth in terms of the number of cards she gets, proudly displaying them on every surface of her sitting room as proof to visitors that she 'matters'. I wouldn't dream of not sending her a card for every birthday, Christmas, Mothers Day and so on, but I also go to visit her on the day, or at least phone her to wish her happy birthday if I can't get there in person, and to me that's far more important.
I don't send them to friends though, and friends don't send them to me. We do remember one another's birthdays, and usually send WhatsApp messages or FB congratulations instead. These still say that we've remembered one another, but are a lot less fraught than sending cards. People are generally much more busy than they used to be, and sending cards means remembering days in advance to buy one, get a stamp and post it in time. Even then, the odds on it getting there on the day are slight, whilst a message or text is instant, and the sender has a 24 hour window to get it there on time.
If someone chooses not to use WhatsApp or Facebook, or be able to get texts, that's not the fault of the senders either. Nowadays all of those things are easily available and have been for so long that most people have access to them.