I would never say irregardless just like I would never say ”conversate”. I found this which may help clear things up:
Dictionaries today are descriptive. They don’t tell you how to use the language or which words you should and shouldn’t use. Descriptive dictionaries simply note the ways language is being used by people. That’s how words like emoji, clickbait, and meme can get in there, and that’s how irregardless got in there as well.
Granted, lexicographers have a way of noting that some of those, let’s call them unusual words, are not words an educated language user would use in formal discussions. Dictionaries add a “nonstandard” tag to such words, and they stay nonstandard until they gain enough traction to be included among the “standard” words. In case you’re wondering, irregardless is a nonstandard word.