Blame the Bearded Ones for it: http://encyclopedia.laborlawtalk.com/Lumpenproletariat
Actually, it is an analytically useful term which introduces some refinement into the catch-all notion of the working class. It corresponds to their concept of class consciousness as a key defining characteristic of the working class. The lumpenproletariat does not have it hence it is not a part of the theoretical construct "Working class."
I think that the concept has a clearly defined meaning as well - you can distinguish a lumpen from a proletarian by observing their behavior, e.g.:
Proletarian - belongs to a working class organization (union or party or both), expresses solidarity with members of his class (e.g. does not scab, supports labor action abroad); forms alliances based on his class interests rather than on ethnic, national, cultural or religious identities;
Lumpen - cares only about his own interests even at the expense of members of his class (e.g. he is a scab), supports the interests of bourgeoisie against interests of working class abroad (e.g. jingoism, patriotism, foreigner-bashing), belongs to bourgeois or reactionary identity organizations such as religion, or NRA, scoffs or fights unions.
Emancipation? I do not know if anyone came with a good idea how to emancipate a lumpen. Bat'ushka Stalin tried by creating a vanguard party as the carrot ad gulags as a stick - but did not get very far. Methinks it is a lost cause trying to save people against their own will. Like in any twelve step programs, it must begin with a person standing up and saying 'My name is so and so and I am a lumpenproletrian." Those unwilling to make that step cannot be helped and may be as well written off.
Wojtek