@gabrino. It is a good observation you make there; one I don't recall seeing here before.
It can irritate my wife too, and she's SGn. We've had instances where my wife asks a question, the reply is directed at me, but due to the mangled accent I can't understand it. Then I have to look at my wife with 'that look' and she'll repeat it to me in English. It can get a little surreal, but usually it just amuses us as it happens pretty often.
The other thing that irks my wife in SG, is even if my wife is treating me to a meal out, and she asks for the bill, the wait-staff will almost always hand it to me, or place it by me.
It's not just SG, it seems just how it is outside of 'the West', patriarchy is much more ingrained. As PNG suggests above the concept of gender-equality has yet to arrive in much of the world. SGn society is perhaps less modern than their 1st world infrastructure suggests, perhaps why these instances tend to surprise.
Another example: Checking into hotels just about anywhere outside of EU/North America [US/CN]/A-NZ. Even if the booking is in my wife's name, the receptionist usually speaks to me. In which case I just turn to my wife, give her a palm-upwards gesture 'over to you', and keep looking at my wife until 2-way conversation without me is established.
- I think two other things perhaps feed into the matter. There is a religious aspect for Muslims. You might not appear to be a Muslim, but it might be that it adds to setting a pattern for how everyone is treated.
- An age thing. There is still [IMO] notable deference given vs age in Asia. So if your husband appears older than you, together with the above causes, the result is what you see.
Suggestion: In such situations, when you ask a question have your husband looking fixedly at you rather than the clerk. And if not permanently at you for the entire interaction, then out the window or something, anywhere but at the clerk. I reckon that should do it. Good luck, and good question, welcome to the forum!