It's because these people who have learned that there's lack of opportunities in the rural areas need to find it on the urban areas.
And that's why they migrate and they know what career they have to take. Some are only taking risk by doing that because not everyone gets the success from migrating to the urban centers.
Speaking of migrating, there are also international students that know there's more opportunities to them if they avail that program of going to school their desired country which has the path for them to have a working visa and then permanent residency.
Of course, everyone knows that there are a lot of job opportunities in the city and in a developed country. Down here in my country, people are not just moving from rural area to urban area to look for jobs. The ones in the urban areas are traveling overseas to a better country where there are more job opportunities than in my country. It's a norm since people need to plan a better life for their family.