I simply don't want to memorize 3 or more different versions of the syntax codes.
Sometimes I'm using .Net. Sometimes I'm using Python. Sometimes I'm using whatever oddball engine the developer chose.
I know how regex works. I can use forward and backward references. I can combine complex patterns. I can match, extract, replace, transform, etc. Sometimes I have even used nested patterns (though I'd probably need half an hour to re-learn it well enough to read one). But I'm not sitting down and memorizing the difference between /d and /D, or \S and \w or any of that. Frankly, I'm very lucky if I remember the difference between ^ and $. I will have the .Net[0] and the Python[1] doc in my bookmarks forever.
I'm not remotely ashamed of it, either. The codes are completely arbitrary with absolutely no intrinsic meaning. Worse, it's not easy to tell the difference at a glance between literal characters, character classes, operators, wildcards, special constructs, etc. More than once I've been confused by a regex only to discover it does something I didn't know they could even do. Regex patterns are meant to be concise and comprehensible to the regex engine, not to the programmer.
Don't feel bad because you don't memorize an arbitrary and complex syntax. Memorizing syntax is not the job of a programmer. The job of a programmer is to compose the logic and design the system and know that a syntax exists to compose it in. A programmer is an author, not a linguist.
[0]: https://docs.microsoft.com/en-us/dotnet/standard/base-types/...
[1]: https://docs.python.org/3/howto/regex.html