Symphony's architecture was first concieved back in the 2000's and it's now starting to show it's age. While the architecture works, and works quite well for simple sites, and those that don't need heavy integration, it starts to have obvious flaws and gaps when trying to use it in a more modern way.
Back in 2009, cloud hosting was in it's infancy, PHP frameworks were few and far between and PHP itself was not as powerful and natural as it is today.
It's time to rethink the architecture, and think about how it should be in 2014.