Sometimes people from other cultures think that Spanish people are not polite because they don’t say “please” and “thank you” as often as other people from other cultures. Politeness and kindness are expressed in different ways on this planet. In Spain, people often use the imperative for asking for something (“Give me this or that”), but their voice, their gestures, their humo(u)r, the famous “diminutivos” (a suffix that makes words “little” in a good way, like “-ita”, “-ito”, “-illo”, “-illa”) when it’s not a sexist use) often express politeness (Thanks, María, for reminding me of diminutives!) So not using “please” doesn’t necessarily mean you are being rude. In Spain, it’s kind, it’s polite to say hello and exchange a few words, even when you are a customer, when you want a good or a service.
On the other hand, Spanish people also have the feeling that some foreigners are not polite. And here are some examples to illustrate why. When at the supermarket, foreigners living here, or spending their holidays here, are incapable of saying “hola” (hello), “dos bolsas, por favor” (two bags, please) or “gracias” (thank you) to the check out person. Even if Spanish-speakers try to speak English it is always kind, or polite, for foreigners to learn a few words at least. It shows you feel some basic respect for your hosts, or at least that is the feeling those hosts might get. Not saying a word in Spanish feels like when you travel abroad and reject food people offer you. Food is culture, and when we travel we need to be flexible and never say no to food that is being offered (unless there is some kind of problem, of course) because it feels as if you rejected the culture itself, its people.