Reason for selling is...

The item I own is really not worth what I paid for it.

I do it just to show someone that said I couldn't that I can. For instance my wife says I can't sell my dog. So right now I have a 2005 pure bred boxer for sale. It is a one owner and has all the upgrades you can possibly have. I have kept it in a smoke free, kid free home. Yea I don't sell that stuff, I give all the smoke and kids away for free. Also because I know you will say you can't sell that it is mine, I am the guy that lists an item that you might you have for sale on the 'gon here a few lines above yours at a slightly higher price. Even though you won't take low ball offers I will. I do it because I can.

*The seller has a significant information advantage over the buyer; just wait until cars from NY and NJ start showing up in used car lots. That being so, it seems to add insult to ignorance to give a reason for the sale, since buyers have no independent reason to believe it, and every reason to doubt it (i.e. the seller is trying to make a sale after all)*

There's a whole lot of truth in what you're saying, & why I think it's so useless to ask "why are you selling". Buyers IMO should be asking about the condition, history, any damage, etc. But it seems a lot of buyers think the way to ascertain all that is to ask "why are you selling".

I don't think I've ever asked that as a buyer, but for sellers who've been asked "why are you selling" dozens of times, it's just way easier to address that in the listing. So I don't see sellers as being in the wrong for listing that; I just think buyers who think asking that is the most crucial thing to ask are off-base......

Reason for selling is, "upgradeitis"

I have never been asked why I was selling, and have never asked a seller. I have liked almost all the gear I sold, just like upgrading or changing.