Why do they love it? We suspect that, at some point during the development of Assassin's Creed, the developers at Ubisoft decided they needed some way to make things a bit more X-TREME. And since Altair with a BMX bike would have been a little silly, they had to find another extreme sport that fit more readily within the context of brutal-yet-subtle-murder. Thus, parkour suddenly became THE way to get around in games, and apparently it's never going to go away, no matter how little sense it makes.
Case in Point: inFAMOUS
Seriously, why did having electric superpowers make Cole really good at climbing things in inFAMOUS? Couldn't they have at least come up with some kind of silly lore-driven workaround, like those micro-fibers on Spider-Man's fingertips?
Why do they love it? Unreal Engine 3 has become so synonymous with big-budget Western games that simply announcing you'll be using it gets your game headlines. Developers don't use it because they necessarily want to, but rather because using Unreal Engine 3 automatically guarantees the game will be considered "graphically superb" by a gaming world which dubs that which is shiniest, best.
Case in Point: Damnation
When Gears of War pioneered the “Unreal Engine 3 look” on consoles, it inspired years of wannabes to come chasing after its coveted aesthetic of “dirty and gritty, with a thick coat of saliva.” Damnation is a prime example, aping the weathered look of the Gears games, but none of their playability or charm. It’s also proof that “Unreal Engine 3” doesn’t necessarily mean “good-looking,” as anyone who’s seen it running for more than five minutes can attest.
Why do they love it? A game developer who mashes two genres together reeks of the same desperation as a starving gamer running to the fridge at 2 a.m. only to find it barren. A developer who exclaims, "platforming-first-person-shooter-adventure-... MMO!" is just like that starving gamer, who in our example goes on to craft the curious culinary concoction of stale spaghetti with mustard and a Powerbar on a sesame seed bun. We can all agree that it was... interesting, but most of the time we end up swearing we'll never try it again.
Case in Point: MAG
OK, so, wait: Each game is like an RTS, but only for one person on each team? And that person gives orders to a bunch of sergeants, who are playing an RTS/FPS hybrid? And those sergeants then relay commands to 230 other soldiers, who are playing a pure FPS? And it's sort of like an MMO too?