Sort of like the internet :)
Most places have no solicitation laws and other privacy laws that do make spam illegal.
You also neee to count in piracy and general violations of copyright laws; you'll be surprised just how much content on youTube is illegal search for "full movie" or "last week tonight full show" and you'll gea quite a few legitimate hits.
Like it or not from a logistical point of view illegal content makes up the bulk of the traffic, that said it isn't any different in any other field if we take global shipping then illegal arms and drugs probably make a nice chunk of global shipping (revenue wise) there also it doesn't mean we need halt all global and local logistics operations.
Once you take both out of equation, the cases of content either abandoned by owners or reasonably old will take more than 5%.