i would say the biggest reasons people dive lakes and quarries is for certifications and practice. Its calm, relatively clear water (depending on the individual body of water), no currents, and no tides. These are perfect conditions for new divers who may already be intimidated by the gear and the idea of going under water. They get the chance to practice their skills and get comfortable before their first salt water or moving water dive. Some divers just cant get out like they want to and want to keep practicing so as not to lose their edge. Others have bought new gear and want to learn all the ins and outs before they hit the ocean with it. theres nothing like jumping off a dive boat with new gear and seeing it sink away because you didnt use it or secure it correctly. or seeing it break. or having an uncontrolled ascent because you didnt test it first in controlled conditions. its basically like going to the pool , but better. sometimes they offer lots of plant/animal life, sometimes its ledges, caverns, or caves, and lots of times it planes, cars, and other stuff. if you dont like the quarry, thats ok. if you do thats ok too. the one thing that I`ve learned in the last 2 years is that as long as you put safety first, diving is all about personal preference.