Only the pieces that are visible enough to be still recognizable make it into photos in news articles. The real data is very different, especially when you are looking for the micrometer-sized plastics that end up killing fish or getting into bottled water.

Also I noticed the term "microplastics" is used for two different things - one are fragments of plastic size 1-5cm, the other is the size of glitter particles and smaller. It is the second one that's more of a concern.