The (insert here) only has to fail one time for it to be a serious problem. Just one time. Just because you have never seen one fail does not mean that it can't. They have and it has been documented for years.
Insert here = your choice
"extractor rod loosening"
"trigger return spring"
"battery for laser sight"
"loose adjustable rear sight"
"debris under extractor star"
"bullet creep"
Another vote against the lock.
Too many documented reports of it coming on unintentionally when shooting the gun. With today's gun care products rust prevention is not a issue unless you just intend to never care for it.
Citation?
Bingo!.... I think most people don't like it simply because it's not needed, they'll never use it (I sure don't) and they resent what it represents (government intrusion into the design of firearms)...and it's ugly of course.