Here's why:
* Microscopy limitations: Linnaeus's work relied heavily on the ability to see organisms with the naked eye or with simple microscopes. Archaea and bacteria are microscopic organisms, too small to be seen with the technology available at the time.
* Understanding of life: In Linnaeus's time, the concept of life was much simpler. He categorized organisms based on visible characteristics like shape, size, and habitat. The differences between bacteria, archaea, and other life forms were unknown.
* Development of microbiology: The field of microbiology, which studies microorganisms, emerged much later in the 19th century with the development of more powerful microscopes. It was only then that scientists could start to distinguish between different types of bacteria and later, in the late 20th century, discover the unique characteristics of archaea.
It's important to note that Linnaeus's system of classification, while based on limited knowledge, was groundbreaking for its time. His work laid the foundation for modern taxonomy, and it continues to be used today, albeit with significant modifications to accommodate the discoveries made since his time.
