Vertical Decorative Concrete Theme Wall
The problem with proportioned bagged mix is that it is uniform, but may not be the ideal for the actual application. The modern "factory controlled" image sells well as does the uniformity.
One of the problems with a proportioned bagged mix in the U.S. is that the properties of the mortar depend on the local aggregates that care used. The cement is very uniform as are the admixtures and lime (if used). The cost of shipping restricts the aggregate to local natural materials. Sand for mortar can be critical depending on a combinations of gradations (maximums, minimums, average size, etc.) and most importantly, the particle properties (smooth, rough, angular, rounded, etc.) and the type of fines (or dust) that can also be fine rounded paticles or flat plates.
When you go to use a mortar that requires workability and adherence(stickiness), you may have to make additions of cement, lime or clay to give you what really works. Strength is not a factor in most situations when you are dealing with veneer.
The other Schu - Dick