I despise the meager salaries university graduates receive after long years of study. They receive paltry salaries that are barely a fraction of what an average construction worker earns with physical effort.
Don't compare so one-sidedly. Manual workers may earn more money but do you know what they have to go through? They have to work 10-12 hours under the hot sun or pouring rain, they do hard work and almost non-stop, or worse, they can have an accident and lose their life at any time. Not to mention, the job is unstable and can be fired at any time, they may have financial difficulties.
Meanwhile, as an office worker, you get to work in an air-conditioned environment, enjoy full insurance, salary, annual leave...not to mention, you will have the opportunity to be promoted with a better salary.
I don't know if there is any difference between our countries, but in my country, most of the poor people are those who have no education or degree. People with degrees may not always find jobs in their field of expertise, but they do not lack job opportunities and can come up with their own business ideas using the knowledge they learned in school.
You have a good point, the future perspectives can be better for workers with university, but also manual workers can be promoted to foremen or similar position.
The conditions for manual workers are not that bad, but after lifetime of manual work most have problems with spine and joints.