Flybuys and Coles gift cards are vastly inferior systems to Woolies.
A. Points not credited instantly
Whenever I qualify for a Woolies bonus it is on my account instantly. If I've been one of the spend X per week for 4 weeks and get $10 worth of bonus points, I've often, on the final week, paid for part of my groceries (enough to get me over the bonus threshold). Then paid for the rest of them with the bonus $10.
Coles takes at least 2 business days to add even the same day's points, let alone any bonus points and it often fails completely (they stuffed up the current 2,000 bonus points on Uber and other gift cards).
B. Balances incorrect
The FB points balance on my Coles receipt is never correct. It doesn't even show the amount I've just earned on the current shop. And the total "from last night" never matches my online total in the FlyBuys site or app.
C. Gift Cards #1
When I buy a Coles egift card I have to keep a PDF copy and keep a written update of how much value is left on it. On top of that there are all sorts of restrictions on where and how you can use them. Woolies egift cards can be stored and used in their excellent app which has balances updated in real time. I can use them in store or online at Dan Murphy, BigW, Caltex, BWS etc. The only thing missing is a QR code or similar for the egift to be read directly in their POS devices so I don't have to type it in. Coles checkout machines can actually read the barcode on their physical or egift cards though many of the staff are unaware of this.
D. Gift Cards #2
So far I've been able to use a Woolies egift card to buy other gift cards in store. Coles actively prevents this - you can't even use FB dollars to buy a gift card.
Coles are actually doing the right thing here…
But to answer your question in general, I assume because they are using old tech/legacy systems…I mean they still call it "flybuys"!