The user agent is useful for debugging. If users of a certain browser never submit a form, the site owner needs to know. Anyway, feature testing and benchmarki

The user agent is useful for debugging. If users of a certain browser never submit a form, the site owner needs to know. Anyway, feature testing and benchmarking can be used to create a user agent fingerprint. Hiding the user agent header just keeps it "secret" for a few weeks until the big trackers all switch to fingerprinting. Just give up on hiding identifying information. The promiscuous model used by web technologies is not securable. For instance, timing analysis can be used to determine which sites you have recently visited.