(Completely ignoring the fact that real name policies are legally dubious as well)
To others, some things that may matter to them may include:
- Trackng down old friends
- Keeping in touch with friends
- Keeping in touch with acquaintances
- Staying aware of what friends and acquaintances are up to
- Keeping friends and acquaintances aware of what they are up to
- Fitting into social groups
- Staying aware of what their social groups of interest are up to
- Or more generally staying aware of cultural events, news, trends, and topics that are of interest amongst circles of people they are close to, or other circles of which they are members.
Facebook is a one-stop shop for a lot of these things. Sure, some or all of them are conceivably possible in other ways, but finding alternatives for all of them would involve significant expenditure of effort compared to just being a regular user of Facebook.
Essentially, you are saying that because it saves you some annoyance, it's a good tradeoff, even if that means that a few others face not annoyance, but actual existential threats of death, violence, imprisonment, dismemberment, etc.
http://violetblue.tumblr.com/post/130440543695/why-im-sittin...
Edit: and yes, participation in Facebook is somewhat optional, but there's a larger price to be paid for not participating than the price of any of the annoyances you mention.