Because it isn't a map, it's a diagram.

have a look at Google maps to double check where towns are relative to each other.
For some perspective:
View attachment 123149
West Byfleet is on the line between Woking at Wimbledon, the SWML. Farnborough is the other side of Woking from West Byfleet. But more to the point, why the SWML instead of going direct via Staines?
Perhaps a better route would be Bolton, Wigan (RM), Stafford, Tamworth, Nuneaton, Coventry, Leamington, Oxford, Reading, Basingstoke, Salisbury.