I'm not sure that, beyond my own thoughts, I give more or less attention to these as opposed to living person's birthdays, but I deeply honor it as my way of acknowledging and more importantly, not forgetting that this [un-birthday] changed my life.
* until they reach nirvana anyway
I do remember her, all the time. But everyone has their own way to grieve, to deal with loss of a loved person. Some order 2 beers at a bar and only drink one. Some do family meetings every year, pull up videos and pictures of great times had. Some like to just remember them at random occasions, reminisce about great times had together. To me, randomly remembering a person means much more than an a deathday.
To me, a fixed date makes it seem like this is the only occasion when you're supposed to grieve about that person.
The aspect of a community coming together to memorializing the deceased and supporting mourners is a core tenant of practice. The week following a death, family and friends come to the aid of a mourner by helping them around their house, providing food and visiting with them to ease their grief. Communal prayer that requires a minimum quorum of people is another way a community supports a mourner. Though many people may process grief in different ways, there is little chance a mourner will lack human interaction throughout their grieving process.
Donating to charities in memory of the deceased is also a common practice. My friend's grandmother passed from Alzheimer's disease and I made a contribution to the Alzheimer's association. I recently heard a story of a Holocaust survivor who's father had passed from asphyxiation in a cattle car filled with people en route to a concentration camp. In memory of her father, she would support other's ability to breath by making donations to supply oxygen tanks to a volunteer ambulance service.
[1] https://www.chabad.org/library/article_cdo/aid/281636/jewish...