[chbint]

Sure, you're actually charged with a crime. And the kind of limitations you talk about do apply.

Even in situations where you could be held in jail, there's a tendency to let you go unless it is impossible to prevent you from jeopardizing the investigations by any other means. For instance, if the only real worry is that you flee to another country, you might have your passport confiscated rather than being held in jail. Likewise, if the worry is that you can use your influence to make others do stuff for you (stuff that jeopardizes the ongoing investigations, I mean), then you might remain at home, under surveillance, and so on.

[edgyquant]

If you’re charged with a crime why is it called preventetive custody?

[chbint]

Because there's an ongoing investigation/legal process and you need to prevent something bad from happening. Typical examples are: the risk of you running away to another country, the risk of you jeopardizing the investigation in any way (say, by threatening or harming key witnesses), the risk of you getting killed by accomplices who are on the run, and so on.

[jakelazaroff]

Because you haven’t been convicted? The way it should work is that authorities are only allowed to jail you before conviction under an extremely narrow set of circumstances, such as posing a credible risk to others.