Pedestrian walking signage on the streets of London is pretty good as well.
One of the challenges with "real locations" is differences in scale. In the case of Boston for example, a bunch of lines come together in a rather dense area of downtown. But then a number of lines (even excluding commuter rail) head off to terra incognito--OK, I exaggerate but into the suburbs or even small cities outside Boston.
Scale is one of the main reasons Harry Beck's map worked. Central London on an accurate map isn't that confusingly laid out at a large enough scale. But the outlying suburbs are just so far away, and the schematic is a lot less confusing for the intended purpose of getting the correct train connection than flipping back and forth between different maps and insets at different scale levels
One of the challenges with "real locations" is differences in scale. In the case of Boston for example, a bunch of lines come together in a rather dense area of downtown. But then a number of lines (even excluding commuter rail) head off to terra incognito--OK, I exaggerate but into the suburbs or even small cities outside Boston.