I'd guess, My bikes get washed about every second/ third week.. They get waxed about every second month.. I have four bikes....My VW Jetta which I very much like gets washed much less than I like.. Biking takes up too much time. By time I get back from the ride, lucky to get grass cut..
What is discouraging about my Jetta, it has a roof rack for my bikes... That keeps it out of the car washes far less than it would otherwise.. It probably gets washed every third week and waxed once a year.. But I treat the Jetta with some respect, it gets lubed equal to my bikes drive chain- considering expected mileage for each relative to need..