In reply, the problem is that Latin has a subjunctive mood and it is commonly used; English has only vestiges of it so we use the conditional tense (I should or, more informally, I would ...). Latin is definitely not English in code. In Latin the difference is between volo (= I wish for, I want in the indicative mood dealing with matters of fact) and velim (I may wish/wish for, I would like subjunctive mood dealing with possibilities, wishes, fears etc. ). Sorry if this is not clear enough but perhaps someone will give you a better reply.
Thank you for your answer. So you're saying that "I would like" means I want the stuff, but not at 100% strength, it's like "it would be nice to have it" instead of " I really need to have it" / "I want to have it now or else"? My poor understanding of this difference may come from English not being my first language, while my own language is really close to Latin.
In French: je voudrais (I'd like) vs je veux (I want).
For instance. If you say "Je veux un café" in a café, it's very rude, as it's a command, it's strong. If you say "I would like a coffee" = Je voudrais un café (s'il vous plaît), it's the subjonctive, it's a wish. It's the polite form for asking someone something.
Quand je serai grand (future: when I'll be a grown up), j'aimerai être médecin. (I'd like to be a doctor: not the future, but a wish, my desire, it's subjonctive as it's not real yet). English would use the future, not in French because it's only a wish, and not a future that is certain.
With the future, it's also possible in French, but it sounds like a certainty: Quand je serai grand, je veux être médecin/je serai médecin.
Translated in English: When I grow up I'll be a doctor.
See, English use the future, "will" as it was a reality.
Subjonctive is very used in Spanish and French, for instance.
It's not, however, clear that Romans actually used the present subjunctive of "volo" (velim, etc.) as a 'polite request,' although it's certainly true that English has "I would like" and French has "je voudrais" plus foodstuffs.
The present subjunctive of volo, in examples I've found, governs a whole clause ("I'd like that you do something "), not a direct object (such as a fat fish, or wine, or bread).