But even if that is the reason, the inference is that if they had made it opt-in, a lot less people would have opted-in, otherwise it would have made no difference.
I mean, assume a perfect world, where every single customer fully understands the benefits, and makes a rational decision to buy or not buy based on those benefits and the cost of the item you're buying. IN that scenario, everyone that ordered would see what was on offer, fully understand it and if they wanted it, opt-in and if they didn't, opt-out.
So a system where you are neither opted-in or opt-out out, but are forced to make a decision one way or the other before you can proceed, would force every single customer to choose.
But no. Instead we have a system where people are opted in by default. Which begs the question of why they are.
So, if it is as Peterb suggested (and I've no idea if it is) and that it was an underwriter's (or insurance company condition) to generate enough sales to make the policy workable, then the clear inference is that by making that condition, the insurance company don't feel they'll get as many, or enough, sales if the decision is left to the consumer to make.
And if that's true, then it's precisely why I, and I suspect a number of others, object to the opt-out - because it is relying on customer inertia to sell something the customer might not or wouldn't choose to buy given if they had to make a decision to buy or not buy themselves.
There is a difference in the psychology. Many people don't like making decisions. If you force them to make one, they may not make the one you want. But using an opt-in, you force someone to decide they want it, and not having it is a non-decision because you can just click-through. Even not having a default pre-selected forces people to make a decision one way or the other.
But the opt-out means that buying is a non-decision. The decision to buy has been made for you, and to override it, you're forced to make a conscious decision to reverse that choice. In other words, changing the default requires making a decision whereas accepting the status quo doesn't, and in a world where many people are decision-averse or even decision-afraid, forcing people to decide results in a percentage of people declining to decide at all. There have been plenty of cases studied where people will decline even something clearly in their own best interest if they have to make a decision to get it because, often, of fear of the decision, fear of that they might be missing, etc. For instance, ever seen the footage of people standing in a busy place (shopping centre, railway station, etc ) trying to give away free money? A good percentage of people walk past, refusing the free money, convinced that there has to be a catch. They can't even take the decision to accept a free tenner when it's waived under their nose.
In my opinion, using an opt-out is a piece of cheap psychological manipulation of customers .... and is a well-known marketing technique. It uses this risk-aversion factor to sell something to people when it's likely a good percentage would decline if they were forced to decide themselves whether to buy or not buy. I certainly covered it in my marketing courses at Uni, some 30 years ago.
So whether it's a decision Scan made, or one that the insurer forced on them, it remains the fact that Scan are the ones presenting this to their customers, not the insurers, so the criticism from me gets levelled firmly at Scan. And I'm disappointed to see such a disgraceful piece of cheap psychological manipulation being used, relying on decision-aversion and inertia of the status quo to sell.