Why Can't I Purchase and Download Mass Effect 2 & 3 From The Canadian Xbox One Store?

The game has never been purchasable through the Xbox Store in any region, due to them being multi-disk games. I'd recommend picking up disk copies or getting EA Access, which is the only way to get it digitally.

No, I haven't bought the game. I wanted to buy it as a first try in the Mass Effect world, because Mass Effect Andromeda is upcoming.

It's the first time I hear that reason. But what I did found was:
http://www.polygon.com/2016/11/7/13552118/mass-effect-2-mass-effect-3-backward-compatible-xbox-one

That's why I started searching, but untill now I didn't find a reason why I can't buy Mass Effect 3.

All 3 Mass effect games are available, backwards compatible, digital downloads on the Xbox 1 store.

No, they are not. Mass Effect 1 is available, but Mass Effect 2 & 3 are not available. I've heard that they are available if you subscribe to EA Access, but I'm not interested in paying for a subscription with EA.

I also wanted to add that, although Mass Effect 2 and 3 are not available for digital purchase they can be downloaded for the Xbox One if you have an EA Access membership as they are in the EA Vault

I liked the Mass Effect 3 ending, I have no idea why people hated it. I guess I could understand, I use a different profile for Mass Effect and have all the DLC, I'm playing Mass Effect 2 DLC, can't wait to check out 3's.