Indeed, I seriously don't get it either, i've never downloaded an "unsafe" torrent without having either a socks5 proxy or a VPN to go through
Also even if there ISP is pretty "relaxed", then i'm much more concerned about the 3'rd party companies that's hired by the industry to track down your IP and forward a letter to you from your ISP, and theoretically suing you by getting a court-order.
Previously I always just used a socks5 proxy(because I have a lifetime subscription from 2012 or something, before VPNs where popular for this) and was content with that, because ISPs didn't care what you did(only the 3'rd party's mentioned above and which proxies protect against), but today i'm a little unsure because even though many places states otherwise, then i've read a couple of articles speculating that some ISP's are having actual spy-equipment installed for the industry, seeing as they are content-providers too so also don't like piracy, and is part of the 6-strikes program just shut down. They said they had the ISP's co-develop and use an automatic system, and then it's up to us to guess what that means, some state it's the letters sending out that's automatic, but others say they have automatic monitoring going on too(i'm guessing e.g. DPI to catch unencrypted tracker/peer announces/handshakes). This would make a socks5 proxy not enough(+ you obviously need to enable force-proxy/anonymous-mode of libtorrent with ltplugin or use deluge 2.0 and enable those directly). Another thing making VPNs better than proxy's, is that you also circumvent shaping(throttling - you can also force encryption in client, but limits' peers then), or other disruptions, like the seed-interruption packets send out by one ISP. Lastly, if having a proper "kill-switch", then it's a fully secure option whereas with proxy's you depend upon the client-author(s) to not have bugs in the proxy-implementation, either currently or some time in the feature after an update of the client.
Also, comcast has been known to work on a technology to spy on torrent-use and display pop-ups and at&t has filled patent for technology for tracking torrent-use and what's downloaded for "bandwidth-measures", so it sounds like true enough, atleast with latest parts mentioned.
I use PIA as cheapest, 2 years for 2.91USD a month with 5 concurrent connections and port-forwarding(scriptable which I need).
I read ipvanish is the fastest if you need the absolute fastest speed, but the speeds of PIA is good enough for me, e.g. on a speed-test I just now made, with and without VPN was 170/34mbps vs 160/32mbps and ping 11 vs 20. I could maybe get better results, atleast ping by going more local and use a server in my own country but am a little paranoid and use a server in a neighboring country to avoid local attention. This speed-test seemed to use a little faster VPN server than last, because last test I did was around 165mbps vs 135mbps, but still fine for me personally.
Btw, if on *nix, then I edited some time ago the last post in the thread about VPNs and best kill-switches(+ split-tunnels), with commands for deluge, now tested and all: viewtopic.php?f=7&t=49883&p=228232#p228232
I love using split-tunnel for VPNs, so it works just like a proxy i.e. only used for the torrent-client, so you get full/best speeds during other stuff, like browsing or whatever. You can of-course fire up the VPN for the complete connection too if wanted, but i've not encountered a situation yet where needing that, though just make sure to get your torrents/magnets from trackers/sites using https, since for those your ISP cannot see what you're trying to download, i.e. your searches are encrypted and only the first part of the url is shown to the ISP, so they do know it's a torrent site/tracker, but not which release you're after, as that is listed further down in the url, so no need for VPN for visiting https trackers/sites imho(and they do have "safe" torrents on those pages too, like linux iso's etc, so no "crime" visiting such sites).
Ohh, didn't meant to be this long-winded, sorry