Hey Robert...
Thats a very good question.. There will be several answers to this...
A big part of the reason, some people don't do eyes,, and Please, Please don't take this the wrong way anyone, because its just an observation and not said to put down anyone...
Alot of people don't know how to do eyes properly,either they can't find them, they don't know what to look for, they don't know how to install them or they don't know where to get the tools to do them.,so, the easiest was out is screws and posts...and hey, theres nothing wrong with it. Eyes can be a real pain in the a$$. Ask me about it, I just installed 400+ of them on some sheaths for Rob Simonich, and I do it with a custom setting tool and a hammer,,all by hand.
Now about posts and screws...
Anywhere you have moving parts you have a weak link. Since posts and scrws are two seperate pieces, I consider them moving parts. Sure its handy to be able to break a sheath down and clean it out, but everytime you do it,, you stress those parts even more and failure could happen.They could loosen, strip, or you could blow a post tightening it. Not to mention changing the very impotant and sometimes very fragile fit of the blade,,which could pose a risk of the knife falling out.
Eyes on the other hand are solid, proven one piece units, and if installed properly, giving the back a good solid roll, they stay tight and Never have a problem.I've blown one eyelet in my career, however have blown many posts tightening them down.
Still I think the main reason is people find them frustrationg a hell and can't be bothered with them. If not done correctly, they crack, split and just give you a migrane. I will say this,, you won't find a single split, or crack in Any of my eyelets, thats one thing I'm Super anal about.Those get cut off as soon as it happens. Also posts and screws are about 4 times the cost of a good quality eyelet...
Again,, for those of you guys using posts and screws,, please don't take this the wrong way, everyone has their reasons why things are done a particular way..
Just my .03 cents.
ttyle
Eric...