The benefit of a fee is very simple. It prevents spam. If there is no cost to making a transaction, then anyone can fill up all the blocks at no cost and at the exclusion of other transactions. When people compete for space in a block by paying a fee then then only the important transactions tend to end up in the block chain.
It prevents spam to a certain extent. In most cases an entity could still spam blocks with low chances of confirming transactions, but even if we know it's a spam transaction, it on the other hand isn't spam at all.
As long as transactions contain a fee, even if it's just a low one, it's still a valid transaction that can't be marked as spam, while in reality it might very well have that intention behind it.
According to you, an important transaction as per the economical sense, is a transaction containing a higher than average fee, with higher overall chances of getting next block confirmations, which isn't always so.
Higher fees don't always translate into 'more important' transactions. It's just how the economy goes.