From the LE side, COST, MAINTANCE, versatility and a unwavering belief in the axiom "if it ain't broke, don't fix it".
You may be over generalizing, in both the "low-tech" and the exclusiveness of the pump gun.
About 25 years ago I wrote a article for a obscure west coast tactical magazine entitled:What's Wrong With the Benelli M-1 Super 90 Shotgun? Here are some excerpts that might be of interest.
1. The most serious problem with the Benelli lays between our ears
It is not a pump! Please don't take this statement lightly. Most of us are more comfortable with pump shotguns, we want self-loaders, but we trust pumps. This same mixture of 'wants' vs. trust must have occurred in 1937 when the first M-1 Grands came into service replacing the exceptional 1903A3. The transition of Law Enforcement from revolver to self-loading pistols consumed reams and reams of paper bitching or praising, for and against, one or the other. LETS FACE IT FOLKS, our minds don't change easily!
It's not a pump, it's a self-loader simply means that we must condition our minds to except the fact that the gun uses mechanical energy "other than our arms" to operate. This is a fact, and it denies us the ability to jam the bolt open or closed by sheer force of " will and arm". This fact denies us the mental comfort of slamming our 870 fore-end home with authority and "knowing" its in-battery, and also, the immediate body alarm that goes off when the fore-end abruptly stops somewhere else.
With the self-loader we think that we can never be sure that it will fire when we need it and we won't know about it until it's too late. This is a false notion, there are easy ways to immediately prove 'in-battery' with this weapon.
3. It demands Periodic Maintenance Service (PMS), to prevent ****-Poor Mechanical Function (P-PMF) I am not suggesting that pumps don't require PMS, they do. I am suggesting that PMS in the Benelli is paramount to its operating reliability. I am also emphatically stating that if you do not perform good periodic maintenance service on this weapon, you will experience mechanical failure. If it's your weapon and your life, shoot only superior factory rounds and best clean your SCATTERGUN.
My rule of thumb is that each time I am done firing the Benelli I will remove the barrel and clean at least the chamber, pull the RAT, clean the bolt face and under the extractor head, and wipe down the inside of the receiver (don't forget the receiver rails). This is a minimum, must do, to prevent P-PMF. You can not be lazy, you can not say tomorrow, just do it!
Remember, in the middle of the gunfight, no matter how strong your ARMS are, forcefully racking the fore-end will not make up for poor PMS of this weapon and that's guaranteed!
So Bella, as you can see this question has been around for awhile, and is STILL a good one.
Good Luck & Be Safe