Why do people care about affiliate links? If someone benefits from me clicking on something then good for them so long as the price stays the same for me.
Because it incentivizes to link to products from which the author can get the most revenue. When a link is an affiliate link, there is a greater likelyhood that the choice of product wasn’t completely neutral with regard to that incentive.
For me, affiliate links can be an indicator that the author's motives may be more skewed toward convincing people to buy things than giving a fair representation of the products. However this isn't always the case obviously.