Why do Americans say “can I have” instead of “please may I have” and rarely say thank you?

I've been America 4 times and travelled mainly places such as new york , florida Orlando, Boston, north conway, cape cod, bar harbor.

One thing I've found really strange is when you guys order food you'll say "can I have?" not "please may I have?" I sometimes hear a "thank you" at the end of a order but commonly not and if the waiter says something like "would you like ice in your drink?" Its something along the lines of "yeah sounds good" not "yes please"

This is not be criticising American i just find it strange but then you guys are large tippers and have a big tipping culture so I guess your saying thank you through your wallets šŸ˜… but I just can't bring myself to not say thank you and please and whenever im in America I get complimented on my manners.

I remember being in a bar once and after I finished my drink i bought my glass it back to the bar and tidied my table. The waitress looked at me like I was crazy and asked what I was doing and said I didn't need to do that. In the uk its very common to be this way even if its dying out now with the younger generations now but its the way I was raised.

I remember being on a bus once too and a little old lady got on and didn't have a seat so I gave her mine she said thank you and another lady told me how sweet that was of me to do that but in the uk thats literally common courtesy.

Im not saying Americans are rude people by all means. Most I've experienced in person are really lovely people and super kind but its always something that I found odd.

I remember being in the cheesecake factory and some women was teaching her son to order from the counter. Me and my husband thought to ourselves "well done her teaching her son to be independent" but then he didn't say thank you or please once and myself and husband kinda looked at each other like wtf. If we didn't do that especially as children we'd had got an arse whooping
Why do Americans say “can I have” instead of “please may I have” and rarely say thank you?
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