Well – because we also want to be debt-free again quickly and lead a fairly frugal life. We have the salary, but never adjusted our standard of living accordingly. We are not specialized or managers, just regular engineers ;-)
And do you seriously believe that an average company in the land of engineers would pay you 4-5k net as a non-manager in a – at worst – deindustrialized country? Keep dreaming. If – for whatever reason – your time at BMW, Daimler, Siemens, whatever ends, you’ll have to start living on a smaller scale very quickly.
You don’t have to paint the devil on the wall, but you should also factor in such cases (+ health bottlenecks, stress, etc). So why want to be debt-free after 20 years, if 30 years would also suffice? And as I said: no one stops you from saving additionally on top of the monthly rate.
The be-all and end-all in business life is liquidity. Liquidity bottlenecks should be avoided at all costs.
Many bankruptcies and distress sales are not the result of insolvency, but merely due to faulty liquidity management.