Would, could, and might are polite because they're past forms. The past tense marks distance from "right here, right now" — and English recycles that distance as softness toward reality and toward the listener. This one idea powers most of English politeness.
距離=丁寧、の変換装置
The Distance-to-Politeness Converter
Will you help me? は「手伝う? 手伝わない?」の直球です。Would you help me? にすると、「(仮の話として)手伝っていただけたり…?」と一歩引いた打診になる。過去形が話を現実から浮かせて、相手に断る余地を渡しているんです。日本語の「〜していただけますか」が距離で敬意を作るのと、同じ仕組みです。この項の「距離」は心理的な距離のこと。be about to のように「出来事までどれだけ時間があるか」を言う距離とは、別の軸だと分けて考えてください。
Will you help me? is point-blank: yes or no. Would you help me? floats the same question a step away from reality — "supposing, hypothetically, you were to help…?" The past form lifts the request off the ground and hands the listener room to decline. Japanese honorifics build respect out of distance; English does exactly the same trick with tense. The distance here is psychological: from the listener, from reality. Keep it apart from the temporal distance that picks between will, be going to, and be about to.
現在形→過去形で一段ずつ丁寧にShift to the past, climb one step
I'd like aなぜ a なのか【初めて出す一つ】聞き手がまだ知らないものを初めて話に出すから a。次に同じものを指すときは the に変わる。 window seat.
窓側の席をお願いしたいのですが。
I want の距離版。窓口・店の標準。Want, at a respectful distance — the counter standard.
Could you say that again?
もう一度おっしゃっていただけますか。
Can you の距離版。Can you, one step back.
Would you join us for dinner?
夕食をご一緒にいかがですか。
Will you の距離版。誘いが改まる。Will you, dressed for the evening.
現在形(直接)
近い・率直。親しい相手に。Close and direct — for people you're close to.
丁寧の would は will の未来形ではありません。will like にすると「将来好きになるだろう」という別の文に崩れます。I'd like to = 丁寧な I want to、とかたまりで覚えてください。
The polite would isn't will wearing a disguise — swap in will and "will like" collapses into a claim about your future tastes. Learn I'd like to as one chunk: a courteous I want to.
I'd like to ...〜したいのですがwant to の距離版。この原理の代表選手。Want to at arm's length — the system's poster child.
Would you like ...?〜はいかがですかDo you want ...? の距離版。勧め方の標準形。Do you want …? with the edges rounded — the standard offer.
I was wondering if ...〜していただけないかと思いまして過去+進行形の二重距離。頼みにくいお願いの定番。Past plus progressive, distance squared — for the asks that are hard to make.
It would be great if ...〜していただけるとありがたいです要望を仮定の世界に置いて柔らかくするメール定番。Parks the request in a hypothetical world — email's favorite softener.
まとめ / Summary
過去形=距離、距離=丁寧。これが中心原理。Past form = distance; distance = politeness. That's the engine.
would / could / might は will / can / may の「一歩引いた」姿。Would, could, might are will, can, may — one step back.
I'd like to =丁寧な I want to。かたまりで覚える。I'd like to is polite I want to — learn it whole.
I was wondering if ... は距離の二重がけ(最上級の遠慮)。I was wondering if … doubles the distance — maximum delicacy.