One point is that processes other than root cannot start services on ports < 1024. That was a sensible precaution computers where big and multiuser, like in a university setting.

However, with single-serving services (e.g. in vm/container/vps/cloud), there is no need for it.

BSD lets you configure it with a sysctl option. But Linux defends that option like it is still 1990.

On NixOS, I patch it like this:

   boot.kernelPatches = [ { name = "no-reserved-ports";  patch = path/to/no-reserved-ports.patch; } ];

  --- a/include/net/sock.h
  +++ b/include/net/sock.h
  @@ -1331,7 +1331,7 @@
  #define SOCK_DESTROY_TIME (10*HZ)

  /* Sockets 0-1023 can't be bound to unless you ares uperuser */
  -#define PROT_SOCK      1024
  +#define PROT_SOCK      24

  #define SHUTDOWN_MASK  3
  #define RCV_SHUTDOWN   1