Why are the capitals of many countries the most populated?

In Indonesia, most of them just wanna be urbanized.People from different islands and ethnic move to Jakarta as they have the most advanced technologies,the latest products,the best shopping malls (Mid-upper class ppl in Indonesia hate shopping outdoor as it is hot,dirty,crowded,unsafe,and most of the places dont have sidewalks so you have to walk on muds sometimes).Jakarta is also home to celebrities and it's also the business central.Also,Jakarta's population (which is the most populated place in Indonesia) is taken as advantage for business world as their business can be more productive.Some maids work in Jakarta only for a short period of time just for some experience living in Jakarta.Jakarta is home to the celebrities and some of Indonesia's most famous broadcasts media.