Why? I have no desire to jump ship to another team. Real fans understand that there will be ups and downs, first place and last place, shit moves and great ones.
You said you are a lifelong Dodgers fan, so I don't see where you disagree with me? It's not like you suddenly root for the Angels or Padres, right?
The bandwagon fans are the guys who like the Steelers one year, and then are spotted wearing Patriots gear a few years later. Or people in Washington who don't give two shits about football, are suddenly rabid Seahawks fans 
No, I understand bandwagoning well, no problem with it at all. I was all about the Angels in '02, and Trout has me wanting to watch again. Did it again with Warner/Rams, Warner/Cards, and now with Manning/Broncs, what do I care? Gives me a reason to enjoy the game again, years after all my old Steelers retired.
Shit, quit the Lakers after Magic retired, too. Hated what they became after with Kobe/Shaq, and didn't care enough to follow anyone else. Haven't watched a game since.
I certainly understand the 'my team' thing, but I just find the "real fan" obsession childish anymore. I'd say it's maybe an L.A. thing, but it's probably just me.
And I know you're assuming, 'Eh, he was ever really a fan to begin with,' which couldn't be more wrong. I was beyond obsessed with the game: memorized careers worth of stats - even rival players, knew personal details, went to every game I could, the whole nine.
I remember watching Grogan connect with Francis on a snowy TV, bro. Then watching the long-necked fuck scramble like Tarkenton the rest of the game. Your boys, before you born.
In fact, just found an old fifth-grade extra credit assignment my mom saved: play-by-play narration (with color commentary and analysis) of the 1980 Super Bowl, Steelers vs. Rams. I understand fandom, trust me.