Leader strength is based as much on the margin of error for nicks and abrasions as it is on real breaking strength. Many anglers feel that the ultrathin leader materials now available do not equal their breaking-strength counterparts because the thin stuff weakens steeply if at all abraded. There is a very long list of things that can quickly change the breaking strength of tippets, which includes the touching bottom, hinging at the knots, scraping on teeth and gill plates and so on. There is a real reason many anglers, especially steelheaders and salmon anglers who cast a lot of bites, stick with the low-tech stuff. It doesn’t have to be terribly heavy because there are few rods which are comfortable to cast that can break anything over 10-pound-test at all.