Why have the animals been given difficult scientific names when they already had tbe easier common names?

The organisms are given scientific names so that

Why is scientific name latinised ?

Why are scientific names of living things considered better than their common names?

The scientific name of common toad is

The scientific name of Homo erectus has been given to :

The scientific name of Homo erectus has been given to :

The common name of pea is simpler than its botanical (scientific) name Pisum sativum why then is the simpler common name not used instead of the complex scientific/botanical name is biology ?

The common name of pea is simpler than its botanical (scientific) name Pisum sativum why then is the simpler common name not used instead of the complex scientific/botanical name is biology ?