The dark web is not a well-defined thing. Often already the torrent protocol is listed there.
Dark web is not for the evil things, and not for the illegal things, it is for the anonymous things. These are not always the same.
For example, posting content to the internet going against the governing ideology of the political system, is often illegal, but it is often not evil.
Or - using the example of the torrent - although it is used mostly to violate the IP laws, the illegal is this violation and not the protocol. Thus, for example, you are free to download free software with torrent (example).
It can be used also as a legal defense against illegal activities. Eavesdropping others private communication is typically illegal, but it is being done quite often. For example, reading this post, your browser opened also TCP connections into the following domains:
- multiple google domains (googletagservices.com, google-analytics.com)
- possibly others what I could say only after deactivating my adblocker
Sometimes we all have enough reason to defend against this, to overwhelm the system configuration cost of the tor.
Identity protection is required not only against some "big companies", but it may be needed also against closer attackers. For example, to circumvent some nasty rules/settings/actions of our network provider.
Because from the point, that they are trying to steal1 user data, the darkweb user becomes the defender and the Big, Secure Company becomes the attacker.
1 A lawyer could say, that by clicking some popup on the first visit of some websites you allowed the content provider to steal your data. However, no one can read all the related "general terms and services" and interpret it from the legal system of the home country of the content provider. From this moment, doing this is a misuse of the position of the user, and an "agreement" based on compulsion is invalid.