Why is Dragonball Z (series) not available on legal streaming providers?

I wanted to ask why Dragonball Z doesn't offer legal streaming services? Because there's not on Netflix, Prosieben Maxx, Wakanim, crunchyroll and so on there's Dragonball Z Kai or Dragonball Super and the question is is there a reason why there are no legal streaming providers?

There's a lot not available on streaming providers.

So that it can be seen there, the providers, e.g. Netflix, have to buy the licenses for the corresponding countries / regions of the corresponding films / series.

For example, if it currently has a TV channel and does not want to sell it, it can't be offered via streaming. The streaming provider may not want to buy others because it does not consider them relevant or important or too expensive.