Why are our passports not valid for 10 years?

Now Bangladesh government is issuing Machine Readable Passports (MRP). I was wondering why the Bangladeshi passport is not made valid for 10 years instead of 5 years as it is now. To my knowledge, most of the countries of the world have been issuing passports to their citizens with 10-year validity since long. If our government does the same, it would save one from the hassles and inconvenience that one has to face for renewing one's passport every five year. This would also cut down the workload of the passport office and our embassies abroad.
Ziauddin Ahmed
On e-mail