'I've got all the right (ie expensive) kit, so I must be able to do it without actually putting in any thought or effort' (@SRD)
In some ways it's amazing the number of 'new' cyclists that stick with it.
There's the unfamiliar bike to deal with, traffic, rules of the road (maybe better if rider has done a driving test) PLUS the fact that they are unlikely to be 'bike fit' - if even if they are generally/sporty fit, the reality is cycling uses different muscles and requires hands to deal with (probably) unfamiliar brakes/gears.