Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.
Earning wealth is an obligation if the intent is to provide for one's needs and those of one's family or if the intent is to pay one's debts. Earning wealth is likeable if the intent is to help the poor and the needy, to give to one's relatives or to spread good among people. Earning it to beautify oneself and to show the Blessing of Allah on one's livelihood is lawful.
However, if the purpose behind earning it is to amass a fortune to show off, this is unlawful. The rules above concern only money that is gained through lawful means, as anything gained through Haram means is Haram. Again if the person does not give the Zakah of his/her properties, then his/her money becomes impure hence unlawful. Moreover, some people get so busy in collecting money that they try to get it even through illicit ways and/or neglect to fulfill some of the Islamic duties.
Allah knows best.