Here's why:

* Affordable: They are relatively inexpensive compared to other types of microscopes.

* Versatile: They can be used to view a wide range of specimens, including plant cells, animal cells, bacteria, and small insects.

* Easy to use: They are relatively simple to operate and maintain.

While there are other types of microscopes, like electron microscopes, they are much more expensive and complex, making them less practical for classroom use.