This isn't as uncommon a perspective as you might think... But electrification is mostly about increasing capacity for modal shift, not for decarbonisation. The only reason people are banging that drum is that it's the only one government has left them. https://twitter.com/philatrail/status/1334795711767080960

Electric trains are lighter, faster and more reliable - and also have closer performance characteristics. That means they allow the railway to move many more people/things.

Not only that, but procuring diesel multiple units is becoming harder and harder, and given that the Class 66s will be life expired in not too long, we need to be electrifying to avoid procuring a whole new fleet of diesel locomotives for freight, too.

Diesel trains are also heavily polluting in urban areas. They are less accessible because underfloor traction equipment prevents them being low-floored to allow level boarding. They are less comfortable. They cost far more to run and maintain.