I can only imagine Shopify must get a cut otherwise how do you explain so many basic simple features not being native. I just want to be able to send my customers an invoice, but to do that I need to install an App that gives this third party access ...

I'd like to see this as well. We want to offer our customers a one time sample of our product, which feels like a very basic option. I don't want to have to buy an App, which means sharing all our customers private data, for this one function. 

I am seriously regretting moving across from Square Space.

This should easily by a Shopify native function. We want to offer our customers a one time sample of our product, surely we should need ANOTHER app for this. It's bad enough we need an App to send our customers a Tax Invoice!