This is because, in Tails, *Tor Browser* is confined using *[[!debwiki AppArmor]]* to protect your files from some types of attacks against *Tor Browser*.
For example, thanks to this confinement, even if an attacker manages to exploit a security vulnerability in *Tor Browser*, they wouldn't be able to access all the content of your Persistent Storage.
It is impossible to hide to the websites that you visit that you are using Tor, because the [list of exit nodes of the Tornetwork is public](https://metrics.torproject.org/exonerator.html).
The anonymity provided by *Tor Browser* works by making all users look the same to make it impossible to know who is who among the millions of users of *Tor Browser*.
Tails tries to make it as difficult as possible for websites to distinguish Tails users from other users of *Tor Browser*. If it was possible for a website to determine whether you are a user of *Tor Browser* inside or outside of Tails, this would provide a little bit more information about you and reduce your anonymity.
The websites that you visit can retrieve a lot of information about your browser, whether it's *Tor Browser* or a regular browser. This information is called the *fingerprint* of the browser and includes the name and version of the browser, the size of the window, the time zone, the available fonts, etc.
To make it difficult to distinguish Tails users from other users of *Tor Browser*, *Tor Browser* in Tails tries to provide the same information as *Tor Browser* on other operating systems.