Hey i definitely do say ‘thanks’ if someone opens the door for me or lets me cut them in line…cuz im genuinely happy they did. but im not a fan of things like cash registers in stores with little stickers on them which say, “Smile. Thank the customer for their purchase.” gross. ppl say this with a friendly tone, but i dont like people telling me ‘thanks’ as part of a script. i
as for desis not saying thanks that much… if you live in Pakistan for 4-6 months, you will see that they are polite in a different way. just cuz they are polite in a diff way that doesn’t mean they are not polite overall.
Since one can express politeness through verb tenses and endings there [ex. “Tu zaroor aa vs. Aap zaroor aayega”], words like ‘please’ do not specifically have to be added as they are clear in the word form.
so in English, i definitely do say ‘thanks’ and ‘please’ a lot more since we don’t have different forms of address like ‘tum’ or ‘aap’.
as for “i love you”…yes mr lover def said this to me a few times and i was like instamoosh. 
but if he said it everyday, i wouldn’t mind but it would lose its instamoosh quality. like it more when he only says it in those truly mooshy moments.
but if my brother said “i love you” to me, i would be like “what ..are you ok”. u can call it sad or whatever but im too desi here. i feel more loved when he calls me ‘skeletor’ or ‘baj’ cuz i know he made those names specifically for me. so no “i love you” for my bro tonight; i don’t want him to dive out of the window 