Sure, but those people are also retarded and need to be reminded of such.
I think it's partly from what you said (probably caused by too much anime) and partly because they have this strange assumption that life progresses linearly. Like as in, you get a gf and she's your gf for life or something. While meanwhile irl people have a gf, break up, have another gf, break up, have another gf, sometimes marry her, then get divorced, then get a new gf and then re-marry, etc.
Not saying being a serial divorcee is cool or anything but seriously, what level of retardation would someone have to be on to think 31 is too old to get a gf? I just can't wrap my head around it.