That’s interesting because it doesn’t for me as if Safari 15.1, but Chrome certainly does as of version whatever is the latest (and I use Firefox as my default on this machine).

Most browsers will, or to be more precise: I’ve never met a browser that didn’t request to be the default, but there’s usually a point where they stop asking or else a setting to disable that “feature”.

I always use Firefox and have never seen such a prompt. Do you just close the prompt without answering “no, thank you”? Maybe it is waiting for an answer?