We use the verb 'be' in the first sentence because the word 'married' is an adjective. Adjectives (like happy, sad, rich, tired, and so on) need the verb 'be'. They are married. (present simple) They have been married for 30 years. (present perfect). This would be similar to saying, for example, "How long have you been ill?" or "How long have you been unhappy?". In these sentences, "been" is nothing to do with travelling anywhere - it is used to describe a continuing state. I hope that helps.

I have always been tall. I have been married for 20 years. . These seem to be adjectives, with the verb to be? is married, is tall . I have known her for a long time. I have owned it equally long. I have eaten it often. .. These seem to be verbs, to know, to own, to eat. . Is this the difference you are looking at? . Sorry, not an expert.