Primary reasons for offline raiding. Maybe some realistic solutions

[Evir 38]

One of the primary reasons that offline raiding happens, is because if you online raid people, and they are losing, they end up just tossing everything on the ground and it despawns. If you are raiding a base, the territory might matter a little bit, but mostly they want the resources, blueprints, ect. While they do have fun, they want a bit of a reward for their actions. I have had this happen many times, I attack a base and when all is lost, they just start throwing everything on the ground, it is very frustrating to hear the sound of things being tossed on the ground and you still are working on breaching the walls. 

Another primary reason, they simply cannot raid you while you are online, due to mortar towers and mounts with swivel guns attached being very powerful and people actively resisting, they may not be that good at PVP. Therefore to hurt you they attack you when you are at your weakest, it does make sense, but it sucks when you are the weak group and the strong group attacks you like that.

The game does not have good offline protections, the NPCs are pretty garbage when shooting at anything other than ships. Puckle guns suck at actually hitting targets and when they do, they do very little damage, they are also expensive to operate in the numbers needed to actually deter anything other than the 1-3 man crew trying to sneak in and attack you. Swivel guns are really good, but have basically zero range. Ships are so large that building a box around them, is basically impossible unless you dedicated hundreds of man hours to it. even then, you would have a single 10k stone wall that gets destroyed by a handful of cannon shots. This is why everyone builds gateways around their stuff. It is the only cost and time effective way to protect your ships.

Some solutions decent but doesn't stop all offline raiding, make puckle guns super inexpensive to operate (as in the NPC on the puckle takes 1 gold every 12+ hours or something to that effect),  up their damage significantly, as well as make them actually hit targets consistently. Add a new anti-personnel cannon round that doesn't do damage to stone(possibly wood), but does high damage to players, tames and NPCs at cannonball ranges.

Some less popular solutions, that I personally dislike but others really want, just not all of them please! Pick one: Add offline protection, when the last member of your tribe logs off, you are invulnerable after 30 minutes(time debatable) Add the Dark and Light shielding and war flag system. Add a new tier of building that has much higher health and damage resistance that takes hundreds of cannonballs to penetrate a wall, just make them super expensive to produce, in terms of materials required, not super rare only mega tribes can access materials.

[Bullet Force 151]

The item dropping is indeed a problem and has been as well in ARK. The solution to this in my opinion is that the attacking team should be declare a battle or siege 'area' in which any dropped items remain for say an hour or two. This would at least give the attackers time to breach the walls and obtain some loot.

That said the main reasons for offline raiding are simply timezones and strategic. I'm from Australia and when I raid a base on a NA sever there is a good chance those in it maybe offline depending on what time I attack. There is also the strategic factor, especially if you are in a smaller crew it makes no sense to attack when the enemy is at its strongest.