I suppose there could be jailbreaks without prompt injection if the behavior is defined entirely in the fine-tuning step and there is no system prompt, but I was under the impression that ChatGPT and other services all use some kind of system prompt.
Some models do indeed set some of their rules using a concatenated system prompt - but most of the "values" are baked in through instruction tuning.
You can test that yourself by running local models (like Llama 2) in a context where you completely control or omit the system prompt. They will still refuse to give you bomb making recipes, or tell you how to kill Apache 2 processes (Llama 2 is notoriously sensitive in its default conditions.)
I totally get your frustration, it's because you've seen the pattern before. Enjoy the ride as we all rediscover these fundamental truths we learned decades ago!