Typographical errors: In written text, typographical errors, such as misspellings or missing letters, can hinder word identification and comprehension.
Also, if the documents have many misspelling or grammar errors you reviewers will question the ability of you to complete the proposed experiments with precision and accuracy.
They’ll be hungry when they get here. Third person plural, again, if you write this as a contraction, it will show up as a misspelling, but speaking this way is very common.