There are lots of reasons actually. I believe part of it is a cultural thing. Generations of Americans who grew up watching lawyer and cop shows on TV have been conditioned to believe things aren't always what they seem. The guy who starts out being the prime suspect at the beginning of the program ends up being exonerated and the actual perp is revealed. The obvious exception to this is, of course, Columbo. That program would let us know right from the start who committed the murder and the entertainment came from watching Columbo work the suspect until he broke down. People want to look at the JFK assassination as a crime drama. A mystery. They know it just couldn't have been what it seems like. There has to be more to the story. Surely Perry Mason would have gotten Oswald off and got the actual perp to breakdown and confess on the witness stand.

The reality is life is not a TV drama. The guy who starts out looking like the guy who did the deed usually is the guy who did the deed. The JFKA isn't a mystery and never was. The DPD had gathered enough evidence in the first 12 hours to allow Henry Wade to formally charge him with JFK's murder 12 hours after the shots were fired. The case against Oswald just got stronger from there as the FBI developed the forensic evidence. People don't want a pat answer to the JFK assassination. They want something more interesting than a lowly paid laborer with a cheap rifle took advantage of a once in a lifetime opportunity and took out the President of the United States. Unfortunately for them, you can't always get what you want. But that hasn't stopped generations of snipe hunters from looking for a different solution other than the one that was obvious from the start.

The blood and brain matter wasn't thrown into Hargis. It was dispersed forward and upward and Hargis simply drove through it. it's not a difficult concept to grasp.

The country road I live on used to have a bad pothole at one end. When it rained, the pothole would fill with water and I would usually forget it was there. When I drove through it, my windshield would get soaked. It's was not because the water was being thrown backward. It was because the water splashed forward and upward just like the blood and brain from JFK's head. My car was moving faster than the water getting splashed so my windshield would go right through it. Same principle.

    I put more weight into "sworn testimony" vs "interviews". Officer Hargis gave WC Testimony that he ran to that "wall", "brick wall" so as to see atop the Triple Underpass. This "wall" being the wall running down from the Zapruder Perch.  Hargis initially thought that a shot(s) had been fired from somewhere in Front of the JFK Limo. Fired from Up on the Triple Underpass. This was due to the physical reaction of JFK and the blood/brain matter being thrown back into Hargis. Over time, Hargis modified his impressions, but his WC Sworn Testimony stands. He ran to that "wall" to get a look at the Top of the Triple Underpass.

The hole that you've dug yourself into is so deep you'll never see the surface, so don't talk to me about digging holes, Brian.

 I have corrected so many mistakes you've made, then completely ignore.

 Of course Dr. Carrico is talking about the right side of the head! Avulsed means a body part that has been completely torn or pulled away by force.  Look up the word.  And Dr. Carrico is describing what he saw in that area after the bullet exited the top of the head.  So you're going to tell us that the mess I surrounded in red doesn't look avulsed to you?  Why of course not! To you!  You see only what you want to see, and what you "see" is fantasy. Where Dr. Carrico has his fingers placed on his head isn't where the wound is, and I am definitely not saying that it is, either.  Where he has his fingers is where the large skull flap/piece is hanging by scalp, a portion of which connects to the top of the skull.  Funny thing.   Almost everyone who describes JFK's head wound thinks that that massive skull fragment is the head wound, when it isn't.  It's a flap of skull hanging upside down and inside out, facing the camera.

I am not misquoting Hargis!  Hargis never, at any time, said that he was hit by a "force"!  Get with the program, Brian.   Tink Thompson started that crap in "Six Seconds in Dallas" about Hargis being hit with such "force...", and then he inserted something Hargis said to the New York Daily News the day after the assassination to try to make his point. Nowhere at any time during any of the interviews Hargis gave to individuals or groups that have been made public about being struck by head matter with any "force".

Mark Lane started the ball rolling and soon every little anomaly was found which started a landslide
of suspicion. Plus it was  the 60’s , rebellion against establishment, police brutality , discrimination, segregationists. So it was very confusing.