Yup, the only time I cleaned the kettles was installing new sweeps and taking hold of some craiglist buys.
I know what I cook in my own kettle and I DON't know what the "used" kettle prior owners cooked up in it. In my neck of the woods, the melting pot of America, we have a very diverse culture of people and their culinary fares. I clean them really good before I use em and dump the grill grates that has grease and watnots built up on it.