I'm no expert on the topic, but I've also never heard of a case where a seedbox user was sued because of torrenting. As far as I can tell the seedbox providers only ever get takedown requests, they never have to hand over user data or logs. I believe that's mostly because of the jurisdictions they operate in, but some also have restrictions like blocking public trackers.

There are probably a bunch of things that contribute to this. Seedbox providers fighting against information requests, their logs not being as valuable in court, law firms not knowing whether the IP they'd get would even lead to an address (as opposed to IPs of providers they know to be cooperative), the fact that you only downloaded from the seedbox and never uploaded anything yourself, and so on. Torrenting lawsuits are already pretty weak, and adding all this uncertainty probably makes it not worth the effort.