In small talk, yes, be polite and humble everywhere. In science and engineering, I prefer it has some meaning. If you're sure in what you're saying, have data

In small talk, yes, be polite and humble everywhere. In science and engineering, I prefer it has some meaning. If you're sure in what you're saying, have data to back it up, dealt with it before - say straight. If it's a guess, say it is a guess. So I would not spend time guessing was it politeness of lack of facts behind that hedging. Btw, I upvoted GP :)