Why when I add a new worksheet in Excel 365 why does it add 3 sheets?

[faphillips]

As standard new workbooks I create have 3 worksheets. If I want to add an additional sheet by clicking the + after the last sheet or by clicking insert it adds 3 new worksheets. Is there a way of only adding one at a time? I have experimented with restricting new workbooks to one worksheet but that makes no difference. I find this really irritating. Am I missing something really obvious?

Many thanks