A few-ish reasons:
1. The words are combination of different etymologies from different languages with different origins or ages
2. Because English is a natural language, not a constructed one like, say, Esperanto, which was constructed to be a international auxiliary language.
3. English has an alphabetic writing system. It has only 26 symbols to represent 44 sounds that, together, create millions of words. Unlike, let's say, Chinese which has an unlimited set of characters to display meaning.
4. English is morphophonemic language so the way we write words is a code that represents both sound and meaning. Unlike, say, the Serbo-Croatian language where exact letter maps one-to-one with the sounds of the language.
Language is super fun! English is one of the languages with requires a some critical thinking but once you start to understand the roots, it can really open up a lot of fun discoveries.
