Easy maintenance
If you have 1000 pages with the same affiliate link in it and if someday your affiliate link changes, you have to update the links in those 1000 pages. There are search and replace modules and solutions,
Let’s imagine that your affiliate link is an
Thus if someday, this Amazon link changes, you will only need to change the Amazon link in your htaccess file or in your plugin. You will not need to replace 1000 occurrences in your database.
Nofollow
Also, you may decide to add a “Disallow: /a/” in your robots.txt to prevent googlebot to follow the link. This will be like a rel=”nofollow” in the A tag of the product link.
Example: thewirecutter.com
Thewirecutter.com is a popular affiliate site.
A subwoofer has the affiliate https://wclink.co/link/6978/20454/4/37399/546265071.1539417354?merchant=Monoprice
It redirects to www.kqzyfj.com/links/5513721/type/dlg/sid/AgEAAAAAAAAAAJIXAAAAACCPV-8AAAAAW8GlCg/http://www.monoprice.com/product?p_id=9723