You might as well ask them to standardise lens mounts.
The competition in the industry keeps prices down so the manufacturers try to limit a user's choices to their own accessories, although this does not always succeed (witness the constant 'battles' between original equipment manufacturers and third party manufacturers - currently evident in the supply of replacement batteries).
Such strategies attempt to optimise the manufacturer's accountants' 'bottom line' so that they have profits to plough into product development.
I can imagine that standardisation across the industry would see the demise of many struggling manufacturers or at least their relegation to limited product ranges.
For example, you might have one dominant camera manufacturer, another dominant lens manufacturer, another dominant flashgun manufacturer and so on.
When a manufacturer attains dominance there is little further need to compete on price and the accounts' 'bottom line' gets fatter, meaning that you and I pay even more for their product.
Perhaps when one manufacturer gains dominance across the entire industry we might see 'standardisation' but then, again, competition dies and prices rise.
We just have to accept the situation as it is and make as sure as we can that our original choice of self-imposed 'brand loyalty' will give us the products that we are willing to own at the prices that we are willing to pay.