[SamReidHughes]

(I don't know anything about YC applications but) Because it's a useful context in evaluating the people. For example, how low quality certain aspects of the application could be perceived might depend on the person's age -- one being that a 22-year-old isn't going to have much of a resume. Also, if somebody makes certain kinds of mistakes, it's less of a red flag if they're in their early 20's, than if they're 40 and should know better.

[fibbery]

The logic you just proposed is actually illegal in the states when it comes to job applicants, because it disproportionally discriminates against some candidates based on their age.

[jolene_brain]

This is true for employers when considering applicants for a job (as you stated); but, as far as I am aware, YC does not employ any of their applicants directly. Since YC is a private funding group, the equal opportunity protections do not apply to their seed fund applicants. So this is more of an ethical issue than a legal one.

[jclish]

YC makes investments. Startups and their founders are not employees of YC. You are allowed to know the age(s) of individuals that own companies you wish to invest in.

[SamReidHughes]

Actually as mentioned it's illegal for employment, not investment, and also, my suggested line of reasoning would not be illegal, even under employment law. (It's not illegal to interpret a blank resume of a 45 year old in a more negative light than a blank resume of an 18 year old.)