Does it run on 386SX with 2MB of RAM?

Apart from lack of coo-processor (which I understand), I do not understand why nearly ALL modern operating systems(Including Linux since 2.4 I believe) are hard-coding the kernel to not boot under 4/8 MB of RAM, even if it could in theory.

Why there is hard-limit of 4, 8, 64 MB of RAM in many kernels of various operating systems?

Is it fail safe "just to be safe" or because there some internal routines, vector tables that REALLY requires 4MB ram to work?[memory partitions/blocks ?!]

I asked the same question here:

- https://news.ycombinator.com/item?id=26979499 [Why Linux requires 4MB of RAM no matter of kernel size?]