Because Kobe ain't going to be around forever to milk. Kobe was the most profitable guy for the franchise back in 05 surpassing the profits every Laker before him had generated. They charged more for tickets to watch Kobe play with Luke, Kwame, and Smush than Kobe and Shaq, got higher ratings, and made more money despite not having finals runs and being over the tax. They are looking in Forbes own words, the leagues second biggest draw in history since MJ in 3-5 years time. TWC just paid them 5 billion and negotiated an all Kobe block. Jeanie Buss made a joke that Kobe had a down year the year before last because he only generated 80million alone during the season for them (made more last year).
They need a star. Bus's family doesn't have outside businesses. They arent Cuban or the like. Jerry makes money off talent and an image, always has. Kobe sold, Kobe and Shaq sold, Showtime sold ... Bynum won't. The guy has yet to even get an endorsement in LA, and Artest or MWP has gotten multiple. Andrew rubs alot of fans wrong and it's been shown in polls as they have voted on the times and daily news to deal him for Kidd, KG, JO, Melo, and Dwight in the past.
Dwight ain't cut for the same cloth as Kobe. I don't see him being the guy who goes out there and looks at people and says I dont give a fuck, love me or hate me, and then leave it all out there if they boo him. I mean Kobe, Shaq, and Magic have all been booed wearing that jersey in LA but soaked it in and then had them chanting MVP that same game. Dwight however can sell, can provide a name for the fans to get behind, and honestly could be used to lure another talent to the city way better than Bynum.
Im a guy who is content with keeping Bynum, but it is nowhere near the level I was when it came to keeping adobe and letting go of Shaq. I knew Kobe could step into the light and be the man both for the basketball team and franchise. I just don't know about Andrew being there mentally when Kobe walks away or even truly slows down to an all star level and that goes for the whole brass apparently, which is why they would have to bring in another guy with him with a strong mentality and are looking at 2014 to do so.