here, I will just go straight to the point (as I see it that is). I have often wondered the same thing, specially when i drop I peice (which happens less than before). I would say the main culprit is being to focused on a plan or a side of the board and just forgetting the rest for some time. I no longer drop pieces like I used to, but sometimes after weeks of not dropping peices, I will start dropping pieces till I manage to take back control. Here, I would say the second culprit is over-confidence, which leads to laziness. The last culprit would be lack of experience.
This is simply my view on it.
Guys, just don't hang any of the pieces belonging to you, all right? How difficult can it be?
ChessStrategist to me implies to be a solid 1600, and that's good enough for me. When you talk to your neighbour, do you ask him for his rating credentials? This is a writing forum, not a produce-some-chess-moves forum. I haven't played any rated move on this site either in the last two years, but I will refer you to my title as former chess.com player of the month, if you really insist on having my credentials for my trollish comments