I think this issue comes from the attempt to prevent items from becoming even more over-powering. If they'd allowed such items to involve the same ritual-based procedures as most thaumaturgy 'spells', then you could quite easily have 12+ shift items. However by making crafting the only thaumaturgy application that doesn't go via such methods, the +1* bonus from a specialisation is a lot more noticeable.
However, it is certainly the lesser of two evils.
Just another observation. The rulebook at one point, (Focused Practitioner's page?) states it'd be very rare for a Magic-user to be highly rated in all three cornerstone skills (Conviction, Discipline, Lore); yet most Player's seem to ensure their Wizard/other-spellslinger is just that. I'm not saying this is a bad thing, I simply think its worth noting the designers seem to have expected/encouraged less 'mechanics-focused' thought processes.
* Naturally, the number here can be bigger (or smaller) depending on the Practitioner involved.