Central asian countries have good economic relations with Iran and there are no border issues like say killings in Ind-Pak or Pak-Iran borders.
You cite only the example of Tajikistan and its the only CA country language in the
board.
Ever wondered why???? There are at least 1.2 million
Tajiks living in Pakistan...
Tajiks from
Tajikistan have settled in Pakistan due to the economic conditions prevalent in their home country, many have settled in the northern city of
Ishkuman...The country is nearest to 14 kms from Pakistan.
Some facts about Tajikistan
Tajikistan was the poorest republic of the Soviet Union
and is the poorest country in Central Asia as well as in the former Soviet Union today.
More than half of Tajikistan's GDP comes from migrant
remittances.
These are its exports
Apart from that ....the sign board serves well for the TTP fighters who has huge population of tajiks.
Of course Iran has other ports,
but this route involves through Afghanistan and work on the roads have completed and Chahbahar port is the final item.
We are now clearing the path through eastern route from trouble makers ... Iran is securing its eastern borders from any adventurers and there will be permanent setup
like our borders.