It wouldn't be feasible to just transfer cents every time; I'm sure there is actually a transaction cost to Raiz from the banks for each transaction as part of their agreement.
The whole benefit is that it's firstly mobile friendly - meaning a lot of people in the less developed countries with no computers are still able to participate in the equity markets with almost zero barriers to entry. The price of this accessibility and convenience is 2.50 per month. You only have to get one raiz reward a month to offset this cost.
Yes, it's probably more cost effective to just invest yourself but what you're missing is that not everyone is as knowledgeable about how to purchase shares/ETF's etc as people would be on an investment forum. I dare say we aren't their target audience.
The process that you described is just that - a process, perhaps that's feasible for you but many people prefer just to set and forget.
RZI Price at posting:
65.0¢ Sentiment: Buy Disclosure: Held
(20min delay)