It is implied that you are replying to either the poster before you or the topic at large when you post. Quoting someone is used when it is necessary to explicitly show that you are replying to someone/something in specific or to show that you are replying to something that is on the fringe of being related to the topic at hand. Quoting large posts clutters threads without need. If you need to quote someone whose post is large, it is best to cut their quote down to only that which is needed. This leads to more clarity as to exactly what you are replying to and limits the size of your own post. This is not against our current rules per se (they could use some modification for the sake of clarity and thoroughness), but it falls under the jurisdiction of “keep this forum clean.”
Let’s look at a specific example. Bcmaddog quoted a post whose content was roughly 1050px in height. Add in minimal toolbars and that is larger than the vertical height of a 1920x1080 monitor. The content he added to the thread in reply to this quote is a single word:
Now, this thread is dedicated to d42kn355’s mods and d42kn355 just posted a new mod. From this context it is easy to infer that Bcmaddog was commenting in admiration of this latest mod even without the quote being included in his post. Therefore, Bcmaddog’s quoting of d42kn355 failed to add any additional clarity to whom he was replying as well as adding an extra clutter to this thread, which is why I edited his post to remove the quote.