The problem with doing this with logging is that the frameworks usually make it hard or impossible to selectively enable debug logging for just one customer, or

The problem with doing this with logging is that the frameworks usually make it hard or impossible to selectively enable debug logging for just one customer, or just one in a million requests, especially if you want to do it dynamically (which you usually do). These patterns are far more useful than enabling debug logging for everything, because that just creates a spew and slows everything to a crawl. So you usually end up rolling your own sampling that you manage yourself.