The latter half of the twentieth century has spoiled the average science fiction fan, who has come to expect a Ph.D. in artificial intelligence, superstring theory and genetic engineering from the author of an average SF short story. As science discovers or hypothesizes more about everything, the SF fan has begun to demand that such information be used to minimize, if not completely eradicate, the factual inconsistencies within the narrative. Inconsistencies, it must be noted, are to the SF fan what democracy is to Saddam Hussein. SF fans simply have no use for inconsistencies; they don't comprehend the point of their existence; they, in fact, dearly hate all such contradictions. Seeing as how these readers thrive on a sensible infrastructure in practically all their lively endeavors, the above seems to be quite a reasonable concern.
Time travel appears to be highly advantageous, then, in that there exists no particular body of knowledge which the author may conceivably contradict with. Certain theories within quantum physics suggest vague outlines for the behavior of related phenomena, although these are simply theories. A theory, after all, would have been defined as "a long and unwieldy statement or set of statements painstakingly peppered with scientific terms and meticulously crafted as a highly complex, ambiguous and obscure explanation in a desperate attempt to overcome our insecurity caused by the screamingly obvious fact that we have no idea what we are talking about" by Ambrose Bierce in The Devil's Dictionary, if only Bierce had bothered to get around to including an entry for 'theory' in his dictionary, which he never did.
The author will not pursue this line of thought any further.
Time travel, in short, remains one of the few areas where the SF author can utilize his talent as a writer to create consistent universes, rather than showing off with his C.S. degree by churning out yet another cyberpunk novel featuring data smuggling netrunners or whatnot.
To be quite blunt about it, time travel is one of the few subjects in which SF authors can simply 'make stuff up' and get away with it.
Of course, that's being a little unfair. It may not be as easy as simply making stuff up, after all.