Because that download would still be illegal

Of course its still illegal. I'm not saying it's using a seedbox makes it legal to download illegal torrents. It's just legal in the country of your seedbox. So if your seedbox provider gets a DMCA notice, they're going to throw it directly in the trash.

Additionally, between my seedbox and me, is encrypted. So how would anyone know what I download from my private seedbox? There's realistically no way to get "caught." Copyright holders pay people to monitor torrent traffic for people to prosecute and hassle--but the same isn't true for private servers which encrypt traffic.