Maybe those that don't put a preferred age range for their contacts are not too bothered about age, and are willing to judge people on other criteria.
Also, sorry but I fail to see what your post has to do with ageism.
I get more annoyed at those who have an age range then contact us even though we are outside of it, we will not meet anyone if we are not within thier age criteria, we are not hypocrits and don't meet those that are.
I don't want to be "the last boy picked for the team because there was nobody else left"
I do prefer people to put an age range on thier profile if it is important to them because we will not contact anyone whose criteria we do not match and this saves thier time and ours.
But it is not an "ism" it is a sexual preference, I seriously doubt that those same people don't have friends outside thier age preference for having sex be it younger or older, it is the same as size, colour, height etc, some things just don't do it for you sexually.