Personally I find this a very unreasonable thing to accept. Secure (single user) text processing (etc.) is not a hard problem at all and there is zero reason it should create any security risks.

Crap passwords (and security practices) are not pertinent at all here, unless you also argue that Boeing shouldn't really bother to make airplanes with non-lethal autopilot interactions because being killed by a mis-designed airplane is the least of risks to the typical US citizen's life give how obese he or she is.

The pertinent question is: if you are to design a wordprocessor, should you avoid baking sqlite into the design because of security concerns? I think you should. Sqlite is written and tested very well, but it is written in not formally verified C, and using a memory unsafe language for reading potentially hostile databases poses a completely unnecessary and avoidable security risk.