Architectural Technicians, if appropriately qualified (DIT, Waterford IT etc) may become members of the RIAI - so it's not a scheme to get technicians.
Banks/solicitors may seek membership of RIAI for a simple reason;
The title of Architect is not protected in this state at present, thus anyone can call themselves an architect. If an insurance company deems their qualifications or experience reasonable they may grant P.I. insurance, however there is no guarantee of competance here. To join the RIAI one must complete a minimum 2yrs of practical experience, then submit a case study completed building project, attend a lecture course, complete a written examination and an oral examination / interview examination. To the legal profession - these stringent entry benchmarks provide considerable faith in the competance of an individual. Also it means that the RIAI can, to a limited extent, be accountable for it's members actions through it's code of ethics etc.
Believe it or believe it not - no one wants a building to fall down or fail - no one wants to sue - so requesting RIAI membership is simply a means of getting assurance that the firm or individual architect has some recognisable competance. No one wants to use the P.I. that may be in place - they just want to know, in so far as is possible, that the work done is quality work.
That said - I'm not trying to say that all non-members are incompetant, I'm simply saying that membership is open to all suitable qualified architects and technicians.
Personally, I think I would want someone with both qualification and experience that has been independantly verified, than someone who just has P.I. regardless of their experience.
The root of this problem lies in the fact that there is no registration of architects or technicians in the state at present, this however should change in the relatively near future when the titles get protected under law and only suitable qualified persons may call themselves Architects - the RIAI will be the governing body for entry to the register...when the legislation comes into place I would find it hard to imagine any financial institution and definately not the legal profession accepting anything other than an opinion by a chartered Architect or Technician.