I don't wash mine. I knock the dust off, or blow it clean with compressed air. It's a habit I picked up in culinary school. There are some tools that don't get washed, like grain mills, flour sifters, and pasta machines. Those tools will gum-up or jam if the materials that pass through them are or too wet or even remotely wet in some cases.
I know some guys condition their grain before milling to reduce dust and to increase efficiency, so "keep it dry" is certainly not a rule, just a matter of preference. In any case, care of these machines is left to their owners. I haven't used my mill enough times (at all) since enclosing it in a bucket to collect data on how efficient it is. ...and I might not, since I don't want to disassemble the contraption if it gets gummed up or jams.
All that being said, tools at a culinary school are being used in high frequency, with very high urgency. The lemon pepper crusted salmon or filet mignon you have on the fire aren't going to wait for you to de-gum and dry a pasta machine. Hence, through habit: "First, keep him out of the light, he hates bright light, especially sunlight, it'll kill him. Second, don't give him any water, not even to drink. But the most important rule, the rule you can never forget, no matter how much he cries, no matter how much he begs, never feed him after midnight."