In principle, I find interest charged on insurance premiums terribly unfair. If you buy a policy for a year in January, you cannot possibly claim on the element of the premium relating to future months before those months arrive. If you can't claim for the December element of your policy for 11 months, why on earth should you have to pay interest on it from January?
More disgusting than that, though, is the government cashing in on poorer people who can't afford their VED/road tax in one go. Especially considering that older cars generally attract much higher tax charges than the newer, less polluting vehicles, if you can afford to buy one. It's all automated, so it doesn't cost them any more in admin - it's just a way of hitting the less powerful who can't hit back.
These companies/government probably try to justify it as 'giving people a choice' - allowing them to decide if the flexibility of being able to hold on to their money for longer is worth the extra charge to them. In the real world, of course, there is no choice and poorer folk don't have that money upfront to invest/benefit from in the first place.
I think a lot of wealthier folk genuinely believe that poorer people are unwilling to make sacrifices, aren't smart at investing or just aren't good at budgeting. This is the case for some, but many, many less well-off people just never have the privilege to be in that position in the first place.
Great if you can exercise the discipline and self-control to give up buying treats and luxuries to use the money in a more productive way, but when you're struggling to buy the absolute basics, there simply is no leeway or chance to break free.