Why do Muslims marry their cousins?

In 2018 Medium had an article about Muslim marriage customs.

We are not brought up thinking up of our cousins as siblings. In fact, there is a certain “distance” we maintain with our cousins of the opposite sex once we grew up.

We don’t have to marry the cousins we have grown up with as brothers and sisters, and in my personal experience, we don’t. If someone does marry her or his cousin, it’s someone you are not really close to and haven’t shared a brotherly or sisterly relationship.

Almost 10% of the marriages in the world are consanguine. The practice is more common in countries with a predominance of Islamic culture but isn’t completely unknown in other cultures as well. There are many parts of the world — including China, Korea, and some states of US — where it is banned between first cousins. There are cultures which are okay with cross-cousins and then there are others where parallel-cousins are more accepted.

One major objection raised against cousin marriage is that it leads to birth defects in the offspring. Islamophobe pages have used this very insensitively in the past to crack jokes at the expense of the Muslim community. This is not entirely false — studies have shown that the risk of birth defects increases by two times. The risk of a baby having birth defects increases from 3% to 6% when the marriage is between first cousins. However, the same jump in risk is seen while comparing the children born of a 30-year-old woman and a 40-year-old woman. The exaggerated effects of inbreeding that have been played out in the media do not find favour with the scientific community any longer.