The Advantages of Lime Over Cement
Lime-based buildings expand, contract and flex with changes in temperature and moisture. The use of lime also allows damp to be absorbed to a limited degree and then evaporate harmlessly. If lime based masonry is pointed with a cement mortar which is less permeable than the stone (most cement mortars are), then the moisture will be forced out of the wall through the stone blocks, causing erosion in that part of the wall, in frosty weather this leads to the rapid deterioration of stones as the moisture in them freezes.
Both cement and lime based methods of construction work effectively when properly maintained but a hybrid of the two, solid walls with a soft lime mortar core and hard cement mortar pointing is doomed to failure.