only cuz sites make me. i have a seedbox too, but again just cuz certain trackers have strict hit and run rules that make ratios irrelevant. on some trackers, i'll just upload a few really popular torrents that are freeleech from my seedbox and get several hundred gb's or even up to a tb upload. after that i just blatantly hit and run on every torrent. i'm probably one of the all-time leaders in hit and runs on this one asian music tracker, but i'm such an asian pop addict that i keep worrying money will someday be tight and i won't be able to afford a seedbox. this is the most important site on the net for me so i keep seeding freeleech torrents on there at least a few times a week and my stats are sick. i think i have like a 15 tb buffer to play with. however, if they ever decided to ban people on hit and runs based on their history, i'd be banned like a thousand times. how is that fair exactly? if i uploaded 15 tb more than i downloaded then i clearly helped a lot of people download torrents. who cares if i hit and run on like a thousand torrents. the ones i did seed, i seeded like a motherfucker and am probably one of the upload leaders for that tracker. i see the theory for why is the right thing to do and helping the system work so everyone gets good speeds, but i pretty much don't care. if a tracker only goes by ratio, then i'll do what i have to do my own way to make sure i have a good ratio and then i'll hit and run all day every day. if hit and runs are enforced, then i'll follow that rule if i care enough to still be a member. this one wrestling tracker i used to use also annoyed me by begging for money constantly and threatening to shut down if people didn't donate. prowrestlingtorrent s it was called. run by scum. i had like a 700 gb more upload than download. i hit and run for all the years i'd ever been a member and one day they pm'ed me and suspended me for hitting and running on almost every torrent ever. i told them to disable my account and go fuck themselves. all the new wrestling releases are available everywhere else so if they are going to be dicks and make me jump through hoops by enforcing hit and runs then they better make sure to have exclusive content other trackers don't have. they don't have much of that so who needs them. trackers like asiandvdclub i hit and run on all the time too, but also use my seedbox to make sure my stats are good cuz i love that site and there is no other tracker i know of that's like it. i have a 3 tb buffer on that site cuz i care about it. i hit and run like crazy there, but they are cool and go with the established rules of ratio is all that matters. dvd-rs are many gb's and if i ever lost my seedbox then i'd probably use up that 3 tb buffer within 2-3 years.
short answer is only when i have to.