According to the Open Hub website, Linux has 37,016,567 lines of code, but this is small compared to NetBSD and OpenBSD, which have 72,065,568 and 81,902,070 lines of code, respectively.
Is there a reason why Linux has fewer lines of code compared to NetBSD and OpenBSD? I’d like to know.


Your numbers don’t check out, please provide sources. The Linux Kernel has around 40 million lines, the OpenBSD kernel around 7. You might have mistakenly counted OpenBSD/NetBSD as a whole system (the base installation), instead of solely the kernel.