"Equality for anarchists means social equality, or, to use Murray Bookchin's term, the "equality of unequals" (some like Malatesta used the term "equality of conditions" to express the same idea). By this he means that an anarchist society recognises the differences in ability and need of individuals but does not allow these differences to be turned into power. Individual differences, in other words, "would be of no consequence, because inequality in fact is lost in the collectivity when it cannot cling to some legal fiction or institution." [Michael Bakunin, God and the State
, p. 53]" (http://anarchism.pageabode.com/afaq/secA2.html#seca25
A society that gives members resources based on amount of "work" done will result in the rebirth of capitalism. Saying that one person does more work than another will again create a hierarchy (which we don't like) because that is how capitalism works; people assume that they are entitled to more because they see themselves as more important and and have contributed more. The fact that the elderly, the young and the disabled cannot do as much "work" as those who are more capable must be accepted by all members in the society. In turn when those who were doing the most "work" eventually get to a less-productive point in their lives, that same acceptance would be reciprocated.
"From each according to their abilities, to each according to their needs."