Satoshi who created the BTC algorithm probably thought about this, before someone can create a tech as good as BTC they would have thought of many options and how they want their production to work, BTC wasn't supposed to work like the traditional financial system in any way other than the both of them being currencies, this fixed low interest rate would be of no benefit to the BTC tech, and will only create more holders than spenders.

If you want an 'interest' you should probably go into mining of BTC if you have the finances to do so and be rewarded with BTC anytime you mine a block successfully, or you can use the old successful way of just holding your coins. But interest rates will never be a thing, the algorithm has been set already, and only useful implementations are made through consensus.