Basically, because there is no verification&#x2F;validation surrounding caller id - <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Caller_ID_spoofing" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Caller_ID_spoofing</a>