Customs Office Clearance Process

I've ordered a Macbook Pro 16" custom configuration from Apple Turkey, Istanbul. I track the production and shipping of the product which took reasonable time for me. "BUT" it reached to Customs Office Istanbul and all progress halted and waiting for clearing to be finished. Why do you think clearance takes too much time even the content of the package is wellknown and the participant companies are as legit as UPS and Apple?