[jonmb]

What is their perceived benefit of hiring young? They can pay less?

[calciphus]

Probably. Also, this is Iran. There are pretty heavy social and political differences in the under-40 demographic that the employer may desire. For example: perhaps they have female coworkers or managers out-of-country, which is far less likely to be a problem with that age group.

[rhizome]

I doubt it's anything more than a highly regimented social structure.

You see a form of it in the US when you see a job ad for a web developer where the company desires an MSCS in the candidate.