The advertisers are probably choosing to target everyone on FB in that age range, but asking FB to optimize for conversions. Then the FB algorithm finds more people who look like people who are clicking and converting.
Ok, so dumb question. Why _wouldn't_ you optimize for conversions then? Unless you want some immeasurable branding value type lift.
Sorry for the dumb question but if you're implying one particular bidding mechanism benefits from FB algorithmic experience in a way that's meaningfully more accurate (serving the ad to the guy or girl with the condition), why would anyone do anything different?
The advertisers are probably choosing to target everyone on FB in that age range, but asking FB to optimize for conversions. Then the FB algorithm finds more people who look like people who are clicking and converting.