Are you a US Citizen? That might be the reason. I visited US multiple times in the last few years, mostly on the east coast or Chicago, and the CBP agents were okay. The last time I landed at SEA, the agent there was unbelievably rude, all because I forgot to sign some document. All he kept saying was the document was invalid without explaining why, and then asking if I can read English. Asshole. I was tempted to make a complaint later, but I was running late.