What are they, I thought bitcoin transactions were free, if this is because individuals are contributing processing power to the network, I'd prefer to offer that free than have charges.
If there must be charges, maybe there must I don't know, but if there must, why not 0.0000001BTC on every transaction, over time this might amount to significant amounts and could fund full time developers and maintenence.
Who gets these charges anyway, not that it bothers me that much at the moment with no BTCs to trade with.
Every question you have asked is easily answered by reading either the bitcoin whitepaper, or the bitcoin wiki, or any of numerous posts on these forums. I suggest you google for answers to your questions.