The Stone Master is one of the academic Occupations. It's in the same boat as the Techno-Wizard, as it is an artificer Occupation, but instead of items or vehicles the Stone Master specializes in architecture primarily and jewelcrafting as a sideline. As such it--as with the Shifter and the Techno-Wizard--is also very concerned with places of power (ley-lines, nexus points) and has a long logistical train requirement to make the most of his powers; as such, he also requires a great deal of planning and attention to detail from both the player and the Game Master to fully enjoy what this Occupation offers.
The other issue is that, as-written, the Stone Master must be a True Atlantean. While this can be waived--and I recommend that you do so; there is nothing about this Occupation (or, for that matter, the Undead Slayer) that actually requires that your be a True Atlantean--I will presume, for now, that this is not going to happen. Therefore your Stone Mason is always going to be a Human and thus cause some problems for you when dealing with certain bits of the overall RIFTS milieu. That's an issue; your man will, alternately, have to hide the Marks of Heritage or will wield them like a big ol' badge in order to min-max his House status to best advantage. That's yet another detail to track, and it can be bothersome for both players and Game Masters.
As with the Shifter, the Stone Master's powers require a lot of set-up and forward thinking. They, by necessity, are strategic and logistical in their application vs. the tactical applications usually required by active adventuring gameplay. This is another aspect of the Occupation that turns people off of it; when they play a magic-user, they want to pew-pew their enemies in combat and not pull out a gun instead. (For the common man, what you do when you get into a fight is the defining aspect of an Occupation; everything else is, at best, secondary to what most people think is the majority--if not the whole--of actual play- and that bugs the shit out of me at times.) You're playing an architect that can do his own bulldozing, crane-lifting, stone-carving, etc. so think less Gandalf and more Saruman; you're a guy who works best when he can shape things to his liking and makes the time to do so- be the thinker and planner (and GMs, let them).
Because Stone Masters lack the sort of immediate applicability that your standard RPG wizard brings to the table, it's not surprising to see that Stone Masters (as with Shifters, Techno-Wizards, etc.) are more often seen as NPCs than actually played at the table. If you choose to play one, or have one at your table, then don't gimp them out of hand; sit down and work out what needs to be done to make the most of the powers it has, and then dedicate game and play time to making that happen as best as campaign events allow- don't let other players push you around into doing otherwise (which is the last big reason for why this Occupation, as with the others aforementioned, aren't seen often).