Default library and header search paths

Dear FreeBSD users,

I have more of an ideological question.

I'm a C programmer who's used FreeBSD once before, but not for 
programming (back in the freebsd 13.2 days); why are /usr/local/lib and 
/usr/local/include not in the default library and header search paths? 
If ports with headers and libraries are shipped with ports and theyre so 
ubiquitous, why must I manually specify these paths with every 
compilation I do involving a library? When I write on Linux, I simply 
have to just pass -lraylib (or such).

I am aware I can mitigate this with pkg-config, but that feels slightly 
redundant at times (it is after all a port).

Sincerely,
Eason Qin