"Don't you see that the whole aim of Newspeak is to narrow the range of thought?... Has it ever occurred to your, Winston, that by the year 2050, at the very latest, not a single human being will be alive who could understand such a conversation as we are having now?... The whole climate of thought will be different. In fact, there will be no thought, as we understand it now."

This exert reveals the reason for newspeak in the use of the party. It would eventually not allow people to have a means to express their feelings against the party. It would limit their ability to think out.