In The Philippines, you can legally discriminate based on all three. Many job ads ask for a person of a certain sex and gender within a specific age range. I have noticed that quite a few companies basically just copy job ads they have on other sites directly into Careers, which I think is an egregious under utilization of the resource in many cases, but it's their ad.
Not being able to specify the same criteria as they would otherwise could present an employer with a conflict, if a candidate notices that age / sex / gender is not specified in the Careers version of the ad. I'm not sure that Careers wants to put that kind of barrier in front of companies governed by similar laws, which are similar in many parts of Asia.
With that being said, I think more could and should be done to help companies tailor their ad to better hone in on the audience they will receive. I pull feeds from Careers and while I find some of the ads quite clever and interesting, the majority of them really don't make me raise an eyebrow. These companies know how to fish, perhaps Careers could do a better job of helping them bait the proverbial hook.
Then again, I've never seen the employer view, or the process they go through to post an ad - so I'm speculating a bit. Recruiters can be .. difficult to deal with.