Excessive use of the verb “to be” deprives a paragraph of its cohesion, turning what ought to be an expression of a coherent idea into a list of stand-alone sentences.
Consider, for example, the following paragraph, which I found in the foreword to a book about the reading abilities of college students.
The ability to read English prose with ease and understanding is one mark of an educated American. The desire to follow the thoughts of men through the rich and varied forms of English expression is a further distinguishing evidence of cultivation. Indeed, a reading mastery of English prose is probably the most important single outcome of American schooling.1
Using verbs that indicate action fixes this problem.
We expect educated Americans to read well, to follow thoughts expressed in the rich and varied forms of our mother tongue with ease and understanding. Because of this, we regard this skill as the most important outcome of American schooling.
For Further Reading:
'Foreword,' no?