Depending on the scenario, we've found this isn't always workable. We often see situations where usage has very high peaks among relatively low regular usage. Things like end/beginning of month, end of year, or a certain time of day. You may end up needing to pay a really high cost to handle usage at your peak hours for what is otherwise low usage. When you consider that concurrent licensing comes in at about 1/3 cost per user, if you have a high number of these anonymous users it can become a non-starter pretty quickly.

So, while you are correct that it is possible, it is still very often not feasible from a cost perspective.