It's more that doctors and lawyers in private practice will be differentiated from one another due reputation and experience and the good ones will be paid accordingly. Pilots are not, due to various reasons - some of which are seniority systems, collective bargaining, and the fact that adequate is considered good enough.
Two surgeons may be differentiated by reputation - surgeon A may stuff it up 10% of the time and surgeon B 1% of the time. Surgeon B will be head hunted by a private hospital and paid a high salary to keep them. Surgeon A may get stuck in a public hospital paid according to a standard public service pay scale. Same would go for a lawyer.
Pilot A may just scrape through the system and Pilot B may be vastly superior in decision making skills etc. But the seniority system will ensure pilot B misses out on early promotion and collective bargaining ensures they are paid the same. The employer doesn't value pilot B until the day pilot A drives one into a mountain.