If a person with a small account is in need of their earnings, they could just keep them liquid. I do understand what you are saying though.
There are a number of folks that use their rewards for the basics of life. Yet? It is self-sabotage for those that wish to continue earning rewards to un-stake their HIVE and also is not very good for the blockchain itself in the simplest of terms, hence my proposal of scaled fees for everyone.
If we got into a more complicated method, it would end up being like the Internal Revenue Service (IRS) here in the USA. What a mess! Loopholes everywhere!
An example would be individuals that would be transferring funds among multiple accounts to keep them below the 10,000 $HIVE amount to do the pump and dump thingy. Keeping things simple counters these issues, I believe. There will always be loop-holes which some folks will exploit. Our own President here in the United States has boasted about profiting from the technicalities of our tax system.
Staking one's HIVE coins shows confidence in our blockchain and its decentralized applications (DApps). I am currently powering down a portion of my HIVE holdings in order to invest in a HIVE community, @leofinance.
I don't have a great deal of fiat to invest so I am using my HIVE coins. Of course I will not be powering down all of my HIVE as I like to support projects like @theterminal and the monthly HIVE Power Up Day along with other HIVE stakeholders.