It seemed to fit? The viewer didn't need to understand the concepts behind the science. It wasn't overdone; it made for good entertainment. The show worked for young and mainstream viewers and sci-fi fans alike. It even allowed for making-of shows, geared toward children, exploring the 'science behind it'.
A couple of series in, I wonder if the Dr. Who writing and producing team still think it would not work well in the current show and alienate potential viewers that were not sci-fi fans?