TAv enables on-the-fly decisions about shutter speed vs depth of field vs noise (ISO), all depending on the various and many subjects that present themselves whilst travelling - once your fingers know which directions to turn the wheel = maximum flexibility without too much fuss
And reduces the "hurry up, surely you have taken enough photos, it's time to get back on the bus" messages
---------- Post added 12-29-16 at 06:43 PM ----------
Oh, except for when a smidgen of fill-flash is needed - haven't figured this one out yet!