The answer to this question is quite simple, really. I chose to use only quotes from Doctor Who, Merlin, Sherlock and Torchwood because they are my four favourites. I realize this is my personal taste and other might have opinions that differ from mine, but, without meaning to sound hostile, if you are not happy with the way I run this blog you are free to leave.
Also, the very observant ones of you might have noticed the Merlin quotes are more or less in chronological order while those from the other shows come from random episodes and seasons and/or that there are no quotes from the classic era of Doctor Who. Again, I have two uncomplicated explanations for you. I am still watching Merlin, and I don’t take quotes from episodes I haven’t seen yet because I don’t know in what context they are used etcetera, whereas I have already finished watching all presently available seasons from the other three shows. I have, however, only seen New Who, and no episodes from the Classic Who, which is why there are no quotations from any of the first eight Doctors or their companions or enemies. I don’t know if I ever will be watching Classic Who and even if I would I’m not sure whether I would put quotes from it on here because all the other shows are much more modern, but we’ll see.