I think you don't get the idea of design patterns. How many lines was the biggest project you've really worked on?
— 15k LoC
— That's basically nothing...
— Given that it was a kernel that does nothing, its also kinda useless
— But honestly, where the fuck would you need design patterns?
— Because the introduction of design patterns potentially increase the maintainability of software projects over their lifetime. Given that maintenance cost will be around 75% of TCO the decrease in developer velocity might not be even visible, at least from a financial point of view.