More R&D goes into developing a trout rod, since they need to be strong, sensitive, able to withstand freezing temps, able to handle light line, and let's not forget that steelhead snobs (not all steelheaders are snobs, I'm just saying) will pay anything for gear marketing toward them. Salmon rods are generally beef-sticks with lower-modulus graphite and possibly combined with fibreglass, not to mention foam handles versus the cork on trout rods.