Subreddits may be nearly infinite, but good, descriptive subreddit names are not. r/videos is going to get more natural traffic than r/ReallyCoolNewVideos, which is going to get more natural traffic than r/asdlkajflaksjf.
Sure, but it's a reddit joke, because r/trees is devoted to marijuana(which exists because of a protest against bad mods on r/marijuana).
Probably non-reddit folk will be turned off by the name, and not get the joke. And I bet a lot of members of that sub only subscribed because they are inveterate redditors and not because they're interested in the subject.
r/videos gets more natural traffic because it's a default sub. Regardless, making a subreddit isn't some competition. You don't need to be bigger than the subreddit you're forking from.