Rather its in China or the US or any other country the first motive in chosing a profession is how much can one make. They all have dedication to their crafts because that's the only way you can make a good living. Which professions makes more in a country has to do with how that country and society is organized and their views and values. Lawyers in the US makes more because Americans values the rule of law. Its a article of faith in the US. The reason why MD's and others in the healthcare sector in the US make so much money is because the US spends about 16% of GDP on healthcare.
The reason why in China engineers and scientists makes more is because China values science and technology more. This has to do with China's history. When China was weak in these area's China was invaded and humiliated by foreign powers think the Century of Humiliation. The PRC was founded in the wake of the Century of Humiliation. The reason why the Chinese take so much pride in their scientific and technological achievements is not only because of the economic and political benefits that they get from it or that they are finally joining the big league. But it also gives them a sense of security.
It is reflection of the country development stages more than anything else. Supply and demand at work
China is in the mid of building infrastructure, road, housing, transportation, rail, subway you name it
The export economy also need engineer to produce good
So it is naturally need a lot of engineer to do those jobs
As a consequence they get paid more than say Med Doctor or Lawyer. There is less need for lawyer in China now because most of the dispute is settled through arbitration and negotiation. So China is still in catch up mode and it will be so for decades to comes
Us and the west has entered post industrialization where they practically finish building the infrastructure like power plant and no more money for science experimentation like Space program etc. Use cheap outsource instead of building factory
So consequentially there is less demand for engineer
The situation is exacerbate by anti nuclear, environment crusade and war and the 60's expansion of welfare program which make less money available for science oriented program, Union and the rising expectation of making big money for doing manual labor making production in US uncompetitive
And I would say the lazyness of US industrial captain(MBA) to move the value ladder unlike Germany which has one of the highest cost structure in the world but stay competitive by advancing technology and export and keep the good people in the company
IN the 60's there is high prestige being an engineer with all the Apollo program and nuclear industry was booming because people move to suburb from the country side
TV program like "I love Genie" were popular
Outsourcing and and wall street compounded the problem with their obsession of quarterly result forcing company to hire MBA to improve their quarterly result.And wholesale destruction of job security in engineering profession because now engineering is consider as variable cost that can be reduced anytime. Unlike Germany and Japan which consider them as an asset!
So naturally the young people react to those circumstance and consider engineering is not worth effort. Not to mention that engineering is one of the subject that is hard to master
Why bother ?
TV and media also contribute to the demise of technical profession since they idolized sport jock, lawyer , doctor etc
An of course US is litigation happy people where every body sue everybody for the slightest insult
The aging population too contribute to demand for doctor and nurses
So it is many factor