Tor is not a implementation of I2P. They are 2 different technologies with different usecases.
Tor ussage nodes and hops to obfuscate trafics origin while I2P obfuscates the entire network layer. With I2P every nodes IP is know to every node. Wile this is not the case for tor. Thirth hop doesnt know the IP of the first hop.
Also tor is heavily used to access the clearnet while I2P is not designed with clearnet in mind.