I take it you've not heard them then?
Let's say hypothetically that the speakers on the phone sound comparable to your xmini. Now lets imagine that not everyone has an xmini either. Would having high quality speakers for those people be not be a good thing?
I can tell you that the speakers on this phone are a paradigm shift in the right direction from any other phone I've ever heard. They do certainly push up against and possibly even exceed the quality seen from small peripheral external speakers. That is resoundingly a good thing.
And, for those like you who do have things like an xmini, don't tell me you actually like having to carry about/fiddle around with them? The fact that you've gone to the trouble of getting them and they sell in abundance means there is a strong usage case for good quality speakers on phone. Boomsound is a dumb name but the form and function are really great here.
no I haven't heard them and my point is I wouldn't hear them even if I had the phone because I genuinely couldn't care less whether they're any good or not. I'm confident they won't be as good as an xmini as they definitely can't turn out that sort of bass and I don't carry an xmini around because I have literally no usage case for listening to music outside of the house that headphones aren't the absolute best option for. It stays in the house in one particular place in my kitchen.
I'm not trying to say you're wrong and I'm not even trying to say HTC have made any awful design decision by doing this, all I'm trying to say is it makes sod all difference to me whether they're there or not is all!