Keeping the reward low also helps in keeping the number of new Masternodes low.

Many new coins made the mistake of increasing rewards in this downturn and massive dumping, which resulted in hundreds of new masternodes as the price continues to drop to less than 10 dollars.

I have witnessed one particular new coin go from zero masternode to over 3000 in just 29 days.

So increasing rewards does not automatically result in higher ROI.

If you are just investing now, buy enough coins to setup few MNs at current price and wait for the bull market.