The actress Jamie Lee Curtis complained about MW's addition of "
irregardless" because she misunderstands the
purpose of that dictionary: to document and describe
actual language usage. Therefore, if "irregardless" is in wide common usage, it gets added as an entry.
Dictionaries that are more descriptive than prescriptive: The Oxford English Dictionary and Merriam-Webster Dictionary. (e.g. "whatevs", "chillax", other slang, etc added to OED: https://www.google.com/search?q=newest+words+in+Oxford+Engli...)
A dictionary that is more prescriptive (more conservative and avoids adding new non-standard words): The American Heritage Dictionary of the English Language (https://en.wikipedia.org/wiki/The_American_Heritage_Dictiona...)
tldr: most people don't know the underlying rationale of dictionaries
some Youtube links...
deep link of Kory Stamper @ Merriam-Webster talking about adding nonstandard word "irregardless" to the dictionary: https://www.youtube.com/watch?v=uLgn3geod9Q&feature=youtu.be...
Anne Curzan (advisor role on Usage Panel) for American Heritage Dictionary explaining "what makes a word 'real'?":
https://www.youtube.com/watch?v=F6NU0DMjv0Y
[to downvoters: it would be helpful if you state what's incorrect in my post; I don't want to give out bad information. Thank you.]