Wrong.
It’s because the network hasn’t been built in a way to allow it to easily happen safely, and requires a lot of investment to bring it up to that standard. Politics has nothing to do with it, it’s all about safety.
How does network in SW London differs from the rest of south or southeast London? It was build largely in the same era. If other areas could modernize working practices it should be possible in SWR area too. I mean physically and technologically possible, politics might be another matter...
It looks like class 701 introduction will be missed opportunity in that regard. But then the whole process is such debacle it is hardly surprising...
At this stage folks will be desperate to see at least a few more of them in service this year...