MAK, A couple of technical reasons for the bar end shifters are that with a narrow handle bar and a handle bar mounted bag there is the possibility of some interferance when shifting a Shimano STI. Another is that many touring bikes are built using a mountain bike's crankset and FD. Pull ratio is different between Shimano road and mountain FDs which most often, but not always excludes the use of the STI shifters. The friction mode of operation of the FD bar end shifter allows mixing road and mountain groups.

Brad