There are three good reasons for building a tower at London Bridge Station.
London needs to be dense, but dense development is only sustainable if it occurs where the existing infrastructure of the city makes it possible and desirable. Railways and streets on the surface, as well as the underground network below have created a system of veins and arteries – energy carriers similar to that of a living body. A tower should appear at the intersection of those energy carriers. This is exactly what will happen at London Bridge: no public car parking or additional traffic; the population of the tower will use public transportation – energy carriers of the City.
Southwark needs economic revival. Southwark needs to produce new workplaces and bring a renewed balance between the different communities.
Southwark needs urban rehabilitation. We have to generate more permeable street patterns. The railway has always acted as a barrier within the neighbourhood, separating it from the River Thames.
These three good reasons may answer the question of what London and Londoners have to gain from this project. Of course this all depends on how the tower is conceived, designed and built.