I think we must realize what is going on in this thread: some time ago someone just added a (non-working) banker NPC to TMW, probably just for fun, and now people are proposing the most cumbersome ideas (like loosing all money on dead, etc) by how this NPC could be given some meaning. And ideas to provide interest just doesn't make sense in a world where it is not possible to make money out of money by investments. Besides: implementing concepts from the real world (like stock markets) would really make it another kind of game, and doesn't mean the game becomes more fun (in fact it is mostly otherwise). I think one could even better delete that NPC, than spoiling the game in such a way.
However, there are certainly some reasons to have a banker in TMW, and that are just the same reasons as they have in other MMORPGs.
1. You can access the bank account with all your characters, making money and item transfers between your characters more easy.
2. When an auction is implemented, money from sales and items that could not be sold, are automatically sent to your bank account.
3. When you have to much weight, you can store items you don't need all the time at you bank account to loose weight.
With just these three features, bank NPCs are one of the most used NPCs in other MMORPGs.
Finally, I'm not very fond on asking fee to have access to your bank account, although I have also seen it in other games. Especially the newbies will be discouraged to make use of it then. I think there are better ways to create money sinks in the game, like expensive keys to get access to certain interesting dungeons or regions, which is fairly easy to implement.
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