Hashcode — FAQ
Who is eligible to participate in the Online Qualifications of Hash Code?
The Hash Code Online Qualifications are open for students and professionals of all skill levels who are at least 16 years old. Please note there are additional age requirements for finalists. You should refer to our Coding Competitions Terms for the full list of requirements that you have to meet at the time of registration.

TERMS AND CONDITIONS
1.3 Ineligible Individuals.
(A) You cannot participate in a Contest and will be immediately disqualified and forfeit all of your prizes if you are or become:
(2) a resident of, or ordinarily resident in, Crimea, Iran, or North Korea;

So yeah only reason Iran isn't present is they are forbidding them to participate.