It's not really a conspiracy. It's apathy. Yes, pharmaceutical firms make a lot of money out of diabetes treatment. But ultimately, it's a question of economies of scale. The majority of advanced nations have taxpayer funded healthcare, and so it is in the interests of these nations to fund cure research rather than treatment. So I think a cure is likely to come from a state-funded researcher...although having said that, I'm sure most pharmaceutical companies recognise that the moment this cure comes along, they lose a revenue strand. So perhaps it makes sense for them to get their first to at least cut their losses.
The real issue though is that curing diseases is really hard. Almost every single cure we have for any condition involves boosting our body's ability to fight the disease itself. We don't even really know why T1 happens in the first place, which puts us right on the back foot when it comes to finding a cure.
Curing diabetes will be extremely complex. The 'cheat' way out would be for a company to develop a closed-loop pump that relies on consumables for the rest of a person's life. From a pharma business perspective, this would make great sense but they can't work out the dosing algorithm because it's so complicated.
It's a similar situation for the common cold - what we call a 'cold' is actually caused by something like 200 different virus strains so it'd be extremely difficult to find something that worked for all of them.
