Why doesn't Google Translate offer Farsi and Kurdish?

Well... Because no one bothers to translate unfortunately.

Farsi is available now, but the verb types are messed up. It's better than nothing though.

google Translate works by analyzing copies of documents written in both languages and archiving the expressions. For languages that have a lot of material that has been translated in both directions (such as English and Spanish for example with numerous books, scholarly articles, UN resolutions, etc.) the translator program has a lot of material and can begin to pick up nuances in language. While there are a good number of Farsi-English crossover documents, there are not as many and the discrepancies between English and Farsi are far greater than those between English and Spanish. Kurdish is significantly rarer, not standardized, and there is much less material for google Translate to use.