Edits should substantially improve the post that is being edited. "Too minor" is even specifically a reason to reject a suggested edit.
Only changing "how to X?" to "how do I X?" in the title does not substantially improve the post.
Manually editing a post pushes that question to the front page, drowning out any older questions. This is a major issue if we're talking about hundreds of questions.
Even assuming that all use of "how to X?" is bad, doing a global search and replace still would not do anything about any other potential language issues with those questions.
If the questions can be substantially improved, then consider making the title change at the same time. If not, just let them be; they are obviously good enough already.