Because this will break in situations where you have multiple consumers or if there's any sort of redelivery/failure scenario. Ordering only works if there's a

Because this will break in situations where you have multiple consumers or if there's any sort of redelivery/failure scenario. Ordering only works if there's a single-threaded consumer somewhere that processes exactly one message at a time and blocks processing as soon as there is an error of any kind. The amount of scenarios that this works for is probably very small. The footgun is that people don't realize the above constraints and assume that ordering will magically fix a lot of ordering issues (some more examples of this in the rest of this comments section).