Answer:
If you overload a sentence with nouns it is confusing and one can easily end up with a sentence that is incomprehensible. Consider this sentence, for example:
Before she entered her room, Jane checked that her door was not squeaking again, put her books on the bed and then she went to her desk and sat down.
If rewritten with nouns only it reads as follows:
Before Jane entered Jane's room, Jane checked that Jane's door was not squeaking again, put Jane's books on the bed and then Jane went to Jane's desk and sat down.
This really does leave one wondering just how many Janes this sentence is about.