Gleaning was not hard work. A widow or an orphan could do it.
But let's not forget the truth of the matter. Though the Law entitled the Levites, widows, poor, orphans, and strangers to the tithe and gleanings.... Israel often denied this right to them, especially the poor, widows, and orphans. Amos is a prophet who strongly rebukes their officials in the gates of the city for allowing land owners to deny the poor their "right" to glean, turning them away to starve as these greedy land owners wallowed in profit.
Amos 5:11-13
King James Version (KJV)
11Forasmuch therefore as your treading is upon the poor, and ye take from him burdens of wheat: ye have built houses of hewn stone, but ye shall not dwell in them; ye have planted pleasant vineyards, but ye shall not drink wine of them.
12For I know your manifold transgressions and your mighty sins: they afflict the just, they take a bribe, and they turn aside the poor in the gate from their right.
13Therefore the prudent shall keep silence in that time; for it is an evil time.
The "gate" was where civil disputes where heard. The poor were not being allowed to gather in their wheat from gleaning. The land owners were driving them away from the crops to increase harvest and profits. The poor and the widows would in turn go to the gates of the city and appeal to the officials for "justice". The officials would turn the poor away in the gates, not even hearing their case. Amos promises that judgment will follow for this and other grave sins.