I think they are great if its going to be an obvious dirty job, like priming the oil pump, or spraying paints. Mainly because after a nights work, I have to go into the office the next morning. But stuff doesnt just wash off either, your skin is porous, it absorbs. Hands may even look all clean , but chemicals are getting into your system.
In the other hand, your your wearing gloves to adjust points or something, theres a problem