Whys it nonesense for it to sound absurd to have paid off the original value of the house multiple times without paying off the mortgage? If you literally just see it as that, it sounds utterly ridiculous.
I don't need to do the math, I think the reality is silly.
I just don't have the mentality to accept paying out inordinate sums of money for the necessity of a roof above my head, and the rest of the lark.
Look at it from the lender's point of view then. Why should they lend you £40,000 (or whatever it is) and only expect back the £40,000 over a period of 25 years? Their loss would be huge, and even the closest family member would baulk at that proposal.
Would you lend me £40,000 now and let me pay it back, month by month, for 25 years with no interest?
Your reality is, unfortunately, unreal.