Because theres some genuinely bad pings. Trust me I get it, its super frustrating when you ping out that your mid laner is MIA, then suddenly you have vision of them running bot- and they still agro and die bot even though it was super avoidable.
But then theres stupid ass pings that have cost me for following; someone pings a level 9 baron while were at half HP. Someone pings danger when im chasing mid laner through jungle because there 10% hp jungler is collapsing to help his 3% hp mid laner. Someone pings dragons going to respawn while were aced and someones splitting top lane. Our jungler pings for an invade while I'm low HP and the waves pushed in- and my mid laner is MIA.
It makes it fucking super hard to decipher this while you're managing waves, trading/spacing, and watching out for other potential threats. I'm not saying you're wrong, but its not right to assume that just because you spam something that a player is going to respond to your pings, just like how you probably have died/made a bad call despite warning or MIA pings. Shit happens- best you can do is try not to tilt them more after they die to a ping they should have followed.