ProtegeManiac
Headphoneus Supremus
It's the other way around. OTL amps came out so you have a headphone amp with really good voltage delivery for not a lot of money (at the cost of current performance) to drive high impedance headphones.
High impedance were common before because of a number of things, but most common was lower noise and distortion (but then you have to crank it up since amps other than OTLs have the power going down as impedance rises). Part of the problem with distortion though was that it was caused by headphone driver chips like Philips' TPA6xxx chips and the like - ie the kind they put on CDPs, and sometimes in integrated amps and studio consoles - having a relatively high output impedance (unless you really design the circuit to mitigate that), which then affect high impedance headphones a lot less than low impedance headphones. AFAIK it took Fiio to make the E9 or E09K to get that down to 5ohms and now have the latest Philips chip down to 1ohm in the K5.
