Hmm, ah, so the main purpose for single line matching is to save memory
@Johndeep, I don't think that's the (main) reason, just a side-effect. According to the PR I linked above, where it was implemented:
This is the "simple" version of regular expressions, where it cannot match newlines characters in the middle of the expression. This is the behavior of most CLI tools, like grep or sed. Notably a negative range (like [^s]) won't match a newline.