Doubt: why not to use fork directly?

[izmcm]

I'm searching for new ways to detect jailbreaks and many blogs present system with NULL argument to make that, similar to what is done in the checkFork method with fork below

  private static func checkFork() -> CheckResult {
    let pointerToFork = UnsafeMutableRawPointer(bitPattern: -2)
    let forkPtr = dlsym(pointerToFork, "fork")
    typealias ForkType = @convention(c) () -> pid_t
    let fork = unsafeBitCast(forkPtr, to: ForkType.self)
    let forkResult = fork()
    
    if forkResult >= 0 {
      if forkResult > 0 {
        kill(forkResult, SIGTERM)
      }
      return (false, "Fork was able to create a new process (sandbox violation)")
    }
    
    return (true, "")
  }

But I could not understand why not to use fork (or system) functions directly and instead use dlsym to get fork. Is there any reason for this?