In message .com,
Mizter T writes

A slightly wider way of looking at it is this - there are a good number
of people who, as I said, have always been wary of Tube travel for a
number of reasons that aren't terrorism related - be it claustrophobia,
fear of crowds or fear of being in tunnels under the ground etc.

The main reason is almost certainly the difficulty experienced with
those who find negotiating steps difficult. The bus network has been
able to serve that cohort much more quickly than the tube network will
be able to do.

--
Paul Terry