OK, Let’s add a default option not to delete barlines.
“Why won’t Dorico let me delete barlines? Why is it getting in the way!”
OK, let’s make the default OFF.
“Oh, I didn’t know about that option! I’ve been accidentally deleting barlines for years and cursing Dorico!”
OK, let’s just give a warning before deleting a barline instead.
“Yes, I really want to delete the barline. Why is Dorico so annoying?”
I’m being deliberately flippant here, but I think this does represent the problems with these kinds of options. Adding a whole bunch of “safety lock” options that were all off to start with (and therefore probably ignored by most people until they came up against a problem) would be a lot of work for little gain (to the dev team).
If they were on by default, or constantly issuing warnings, then that would annoy more people than it would help. Or people would just get used to clicking through any warning dialog, causing just as many accidental deletions.