If you hash small hash - you will see the reward getting longer and longer very soon.
But in the end, isn't it the same ?
erm no definitely not. let me put it in simple example
say for example eth price would be 200 now
each day you genererate 1 eth for the whole month, you get get 30 eth for this month
your income would be 200 x 30 = 6000
but with difficulty increasing like mad next month it takes 2 days to generate 1 eth assuming eth price is still the same
so you would only get 15 eth
your income would be 200 x 15 = 3000
big difference there mate, and thats assuming price of eth is still the same. if price goes up then voila the uptick in price will compensate a bit for difficulty.
What if the price of eth drops ...