I can attest to this. I always wanted to join the Royal Marines but ended up joining the Army due to a combination of RM recruiting at the time taking ages (it was around 6 months from PRMC to recruit training, and there were no civvie jobs in my area) and wanting to get on tour ASAP. Fast foward about a decade and I actually applied to transfer to the Royal Marines to fulfill the ambition. It took a lot of interviews with my units hierarchy getting talked out of it, but the main reason to withdraw it was the huge drop in pay. It just wasn't feasible to go from a top end, high payband Corporal to recruit pay and then back to the bottom on a Marine (OR2) salary.
As said above, transferring between services is not something you can just do with ease like a unit posting change. It's a massive admin hurdle, that can months to over a year, and you're potentially wiping away any career progression you've already made.
Really appreciate the feedback (good or bad). Thankyou.
Fully understand the logic. I'm sure the Corps loses a good many viable, high quality individuals who would certainly make the grade by a good margin.
The reasons behind the Corps and source Arm/Branch logic, frustrating as it is, are many-fold, I guess.
The source service/branch of the individual are faced with an inreased admin burden which doesn't benefit the unit in any way because they have trained & paid for someone they don't want to lose.
The receiving service/branch (RM in this case) want someone they can train the way they want them to perform. They are wary of individuals who are experienced, have acquired a level of competency and confidence within their previous role who may have difficulties re-adjusting to the inevitable changes and ethos - particularly if members of the training team are maybe younger, senior and potentially less experienced than the individual they are trying to re-train.
My guess is similarly, the reason the Corps accepts fewer than 10% of young officer (YO) 'recruits' through the Corps Commission route is for precisely the same reason.