In English we often have a formal version of a verb such as ‘protect’ and and a phrasal verb version of the verb that has the same meaning such as ‘look after.’ Both versions of the verb have the same meaning. The difference is to do with register: one verb has a formal meaning, and the other is used in everyday speech.
Native speakers use phrasal verbs in their everyday speech. This is because these verbs are informal. To use the formal version of the verb in everyday speech would not sound right. The formal version of the verb is only ever used in formal writing and also in formal situations, such as in presentations or work situations.
You can understand why we have a formal version of a verb and a phrasal verb with the same meaning by understanding something about the history of the English language.
A long time ago, hundreds of years ago, people who lived in England spoke a language called Anglo-Saxon. In the year 1066 England was invaded by a French king called William the Conqueror. He became the king of England and this meant the language of politics and power in England changed. Now all the powerful people spoke French. The peasant, working people still spoke Anglo-Saxon.
Over time the two languages became one language – English. Importantly, however, the split in the language between formal language (that came from French) and informal language (that came from Anglo-Saxon) remained.
We still have this difference in our language between high register words that come from French, and low register words, that come from Anglo-Saxon origin.
Native speakers use phrasal verbs because they are the most natural words to use in conversation. They sound relaxed. For this reason, learning and using phrasal verbs is a good thing.
However, it is a lot of work to learn phrasal verbs as they often have more than one meaning. For this reason, it’s okay not to bother learning them, unless you want to develop your English to a high level. If you want to speak English to a high level, learning and using phrasal verbs is essential.