So many reasons, many are personal. You stated above, "shipping them to the buyer seems so easy when the buyer can email you a paid shipping label with insurance, where as, you just have to fasten the label to a (free) bike box after packaging it?"
OK so before you get to that point you will need to take photos and have a good description of the bike. That is no problem as you would need to do this even if posting an online ad with local pickup only. Now it can get tricky.
So lets say you list a bike like the one above I have for $600 and put in the ad buyer to pay for actual shipping to their destination., a buyer contacts you and after some conversation says they will take it for $600 and pay for the shipping by sending you a shipping label they will be paying for. Now what? Besides being careful about how payment is to be made which has it's own set of possible pitfalls and you must be careful, we will not even get into this. OK buyer then says OK what is the weight and size of the box you will be packing it in. Keep in mind I personally did not like to pack up a bike until I have full payment, if you box it up and deal falls through it is tough to sell locally in a box, or if boxed and another buyer after first sale fell through asks a question about bike it might be tough to answer as you may need to view bike and it is now all boxed up. But anyway, sale has not fallen apart, buyer needs to know box size and weight to get a shipping label. If you are smart you might say OK, send me the money for the bike and I will box it up and send you the info once it is boxed, but here is where it can go sideways in many ways. I have buyer's tell me they will pay and send me a shipping label, then I would box up the bike, send box size and weight to buyer and have them say something like "gee can you tale 3" off the length and an inch off the width as it will be half of what it is with the box size you are using, or maybe they say "wow that much to ship, I don't want the bike". Then if they already paid you hopefully they did not pay you with Paypal for goods/services as then you kind of have to refund them or deal with Paypal if they protest and request a refund, but doing Friends and Family gives buyer no protection and some balk at that if they do not know you. Now I will not even touch on what perils may happen in shipping a bike besides damage, buyer may say pedals are not in the box and you are sure you packed them, or maybe buyer may say you did not disclose or picture a paint scratch on the bottom of the crank. Heck Ebay is at the point when all you pretty much need to say is the item is not as described and state some small defect, then you need to refund all buyers money paid including shipping as well as pay for the return shipping. These are just a few things that can happen even if not sold on Ebay but through a site like this one. I know the vast majority of the time selling a bike and shipping it works out just fine, but personally I have never had a problem with a buyer picking up/seeing and inspecting a bike when doing a local pickup, nothing beats a cash and carry sale. As I said many times before I know this limits greatly the market for your bike especially if you live in a remote area. I would personally prefer to sell a bike for less money locally than deal with the potential pitfalls of shipping a bike. Whatever you do I wish you the best of luck.
Oh, and by the way, I just sold this bike an hour ago, local collector, saw the bike, loved it, made a fair offer, paid, and went home with it. I will be reporting this bike as sold on here in a few minutes.
