I do not understand why we have to pay for 4 cent per transaction tough, isn't that too much? Who decides the 0.0001 should be the optimal miners fee? How come I get lighting fast transaction if I pay 0.01 and I wait 2 days if I don't pay any?
I do not understand why you think 4 cents is too much? Are you trying to send 10 cents transactions around or something?
Any other form of transmitting money will cost way more than 4 cents per transaction. As far as the incentive, yes it is currently 25 BTC per block, soon to be 12.5 BTC around June 2016. At some far off date (2140 I believe) this will be reduced to 0 and the miners will at that point be totally reliant on fees for their income. I would assume long before that fees start to become a larger and larger portion, especially as usage increases.
Still overall this is cheap compared to say VISA, which averages about 3% of the transaction. You might not see the VISA fee on the front end of a transaction as a consumer, but you still pay for it on the back-end via higher prices as the merchant needs to pass along the costs to cover his expenses. Some merchants transacting in BTC will give a discount to reflect this, so purchases made with BTC are the same as those made directly with cash.