It does affect my choice, not because amateurs cannot write good serious history- more that good qualifications can be considered as a guarantee that someone knows what they’re talking about. But there are plenty of other things one can look at for the same purpose- reviews by those with good credentials, history writing awards, etc.

As an example, I recently bought a book about the American Civil War- James Oakes’ ‘Freedom National’. This isn’t a topic I know well, and I didn’t recognise the name of the author nor the name of the university they work at. Their book is making a provocative argument. All that makes me quite wary- this book could be garbage! But when I look into it I find that this book was nominated for an award, and received good reviews from some of the biggest names in that field. That reassures me- even if I find that I disagree with the arguments made in the book, I have good reason to believe that it’s legitimate scholarship.

So generally I want to find some indication that an author knows what they’re talking about before buying or reading a book. But qualifications are only one of many possible indications.