Why doesn't Shopify use my Canada Post account for label creation?

So, it’s come to my attention now that now I have “Canada Post use your own account” working, when you go to make a label in Shopify it doesn’t use that account. It uses Shopify’s account. So when a label is to be made you have to login to C Post and create it from there. Copy paste etc.. $14 turns int $17.53

My question is why why why?

Pay pal does it,

Another platform does it,

So why does Shopify not do it?

I have Clickship set up and it automatically makes the label UPS etc. (for $9 CAD I can add C Post) and they charge in $CAD not $US, why I guess because they are Canadian?

So Shopify I’d like an answer.