marrying more than 4 wives is not culture but its Islamic teaching clearly stated by the Quran with condition following.

"If you fear that you shall not be able to deal justly with the orphans, marry women of your choice, two or three or four; but if you fear that you shall not be able to deal justly with them, then only one" (Quran 4:3).

"He who does not thank people, does not thank Allah" prophet Muhammed (pbuh)