Competitiveness among specialties is cyclical and is based on several factors such as reimbursement, prestige, lifestyle etc. All of these factors can and will change with time. Radiology was not always competitive, nor was derm, rad-onc, anesthesia. At one time psych was a competitive and prestigious specialty so I hear. What happens if the coin flips and the "lowly" fields you mentioned become more attractive and hence become competitive. Should we then increase reimbursement in said specialty since more AOA students are gunning for them?
Chances are we won't even have to do much to make them higher paying depending on how long they are competitive.
Also, you should consider the fact that competitiveness may be a direct result not cause of salary...perhaps psychiatrists made considerable salaries before and thus the profession was competitive.
Back in the 70s and early 80s Internal medicine was one of the most competitive fields due to lifestyle and the fellowship opportunities. many of the best went into it whereas rads/derm were not. Thing is, payment schemes changed, from paying a standard rate and salary to a medicare based pay for procedure. Thus, while some specialties didn't change in terms of income power(neurosurg/plastics) others did...thoracic surgery dropped because of a reduction in number of operations/procedures compared to cards and dermatology went up for similar reasons.
Likewise, neurology isn't so high paying...but its possible that if the system doesnt change, and with the advances being made it could become the next rads/derm.
Back to what you said... 1 of 2 things is possible. That payment is the cause of competitiveness...not the other way around. and 2. even if payment IS CAUSED or created by competitiveness then it most likely will take place on its own...there's no need for anyone to step in. But I suspect you asked this as a rhetorical question to stump me.