In England, "would you like ...?" is an offer, whereas "do you want ...?" is an enquiry. You might hear the offer form several times a day; the enquiry is rarer. We are a polite nation.
And so are the Italians. To be straightforward one says vuoi? and to be more polite one says vorresti? Duo is teaching the first here, and teaches the second elsewhere. There is no justification to use the polite English here.
You'd say "would you like" in English to be more polite than "do you want" here, but it isn't the same as the exact meaning of "vuoi". We are learning the present tense here, not the conditional, which is a later topic.
Indeed, you could use the Italian conditional, "vorresti", for exactly the same reason, although I never heard it in Italy. In contrast, one hears the first person conditional "vorrei" much more often than the present "voglio". So I guess it must be impolite to say "I want" rather than "I would like", but OK to ask "do you want?" rather than "would you like?". In a way, that would be logical: who is doing who a favour?
At the top of this discussion I see Vuoi ...? = "Do you want ...?". Don't mix this up with Vorresti ...? = "Would you want (or in polite English "like") ...?" As for vorrei, learn the conjugation at https://www.wordreference.com/conj/ITverbs.aspx?v=volere, just before vorresti.