Jane Eyre (the novel, not the character) looks down its nose in disgust at the existing Victorian class hierarchy. The characters who are most interested in the trappings of wealth and status are hypocritical or morally misguided, but characters who take poverty on themselves to demonstrate their great moral nature are also mocked. Instead of the normal class structures, Jane Eyre implies that poverty can be thoroughly respectable, as long as it’s accompanied by an earnest desire to better oneself – or at least earn one’s keep. Of course, it’s easy to value poverty and hard work when, in the end, all the right people get the money.
In Jane Eyre, it is easier for characters to be morally pure if they are poor or if they refuse or renounce possible wealth.
Jane’s inheritance brings with it financial freedom and personal independence; without these, she would not be able to bring herself to marry Rochester, because in doing so she would become his dependent.