Desirue, I am in the Uk.
Highly unlikely you will ever shop where I shop
Tbh, the plants I see sold in the US are generally bigger plants. You will notice lots of yours are flowering whereas none of mine will flower for the next year minimum.
A lot of times freshly imported plants can have 2 plants in the pot. I have had it happen a fair bit. Sometimes it's a good thing and you end up with 2 decent plants. Sometimes its really bad in that you get sold a flowering sized plant and you discover it's actually 2 seedlings together to make the plant bigger which means both seedlings are usually years away from flowering.
I really don't know how common it is in the US. In europe it is fairly common especially when buying seedlings that haven't been repotted yet because it makes sense to pot two seedlings together initially. I think the logic is that one should turn out strong.
So with seedlings not all that sprout will eventually turn into nice orchids, genetics will play a big part in it and some just never thrive and die.
Potting 2 together makes sense to make sure one gets strong and if the other one doesn't that ok. Or maybe it just happens by accident sometimes as it is a repetitive task picking out individual seedlings to pot up. I would iangine it would be similar to picking up beads out of a jar one by one and if you accidentally pick up 2...
So if you are really lucky you get two strong ones but that is very rare because two strong ones get noticed.
Whereas two weak ones get sold as 1 flowering sized plant and then you are just stuck with two weak orchids.
Probably more than you wanted to hear. But worth noting, most people assume seedlings are all generally the same. Breeders do try to breed to get good uniformity but there will always be some variance that's why some people like to buy more than one plant to be able to compare which one is the better one to keep.