SP’s go where the money is.
There is money in East but it’s concentrated in Canary Wharf, Tower Bridge, City of London etc hence why you find lots of SP’s in these areas.
West London has more money, more tourists, all major train stations to every other part of the UK & Europe, more people working plus one of the busiest airports in the world.
London as a whole has great punting options in West, East, North and South but West / Central will always be the best.