Ian Jelf wrote:

Although I have some sympathy with such a system, London is so large and
complex (and busy), that charging a supplement for Underground travel
(which is effectively what happens when compared to buses) is I feel
justified in return for the faster journey. (Hamburg has - or had -
something similar for its express buses).

Paris also has no bus-metro transfer beyond the sort of passes available
in London.

Strangely (to me), in Paris, there is in effect a supplement charged for
the buses. One ticket will take you right across the city on the Metro,
but 3 tickets may be needed for the same distance on a bus. I have often
wondered why this is.

--
John Ray, London UK.