What's the point of these codeshares, or codeshares at all?

As a customer, I am always most confused. I buy a ticket on AC, and end up on a UA plane. And vice versa. And I get rapped by US Customs or Canada Customs by pre-filling out the flight number that I bought on my landing card (the night before), if I get it wrong.

If AC wants to market CO flights, and take a profit or loss on operating them -- fine, they should be able to do that through contractual arrangements. Not by exposing the customer to vastly different service standards, fine print, weird check-ins, different bag limits, etc.

How many of our grandma's or elderly relatives have bought a ticket, on, say, AC, gone to an AC check-in counter, and been told to take a hike over to UA, in another building (in the case of LAX, on the other end of the airport)?? Really, its unnacceptable for this to be happening in an industry whose success *relies* upon customer service.

I don't care if anyone responds to my rant or not....but I think industry participants need to sit down and figure out how to abolish code-sharing, and how to make the experience as transparent to the customer as possible. People travelled on multiple airlines just fine before the first AA/QF codeshares came out in the late 1980s.