Uber is a worldwide company and their services are pretty good everywhere. however, Careem company were originally founded in Dubai and they have a good relations with the UAE government. their future seems brighter in the middle east region in general.
There are many different ways people get job in the UAE. For instance, some people have their relatives and friends working in the UAE who hold prestigious positions at different companies. So they simply ask these relatives to refer them for different job offers. Simple.