Some of this like asking why TV networks broadcast reruns. Everyone hates it but it happens anyway. For the true hobbyist, though, nuances are key and what seems like repetitiveness to me may actually be key to helping someone spend their hard-earned miles/points in the best way (for them) possible. One guy out there, and we all know who, has even reviewed every single A380 first-class product out there! Ugh.
My favorite trip report blog posts tend to be those with new spin or new information. Recently, I liked Ben's very funny "La Compagnie" saga and Mommy Points' equally amusing mileage run report last October where she said, "I’ve never been a fan of the mileage run for many reasons, and I much prefer a ‘vacation run’ where you hang around in a city at least for a night or two to actually enjoy the travel rather than do the completely asinine thing of never leaving the airport." I'm not a Mommy Points fan at all but, really, I laugh every time I read that. Pure greatness.
If you make me laugh, I'm going to keep reading.
Edit: Oh, and CMK10, I confess to liking Spirit . . . .