That's not normally what you need for an application format though is it.
I actually consider that a good thing. Doing everything in volatile memory until user asks otherwise is a relic from diskette era.
For example: cut some content from a file to paste it somewhere else. Now the program saves and system crashes.
Well, it depends what you mean by “need”. But continuous, incremental updates generally provide a much better user experience, either instead of or in addition to active “save” actions.
So, yeah, I think its exactly something that is commonly desirable in a file format for maintaining application state, even if there is a different interchange format that the application produces/consumes as a static input or output.