The semantic difference is not small. "Would", using the subjunctive, implies that the "want" is theoretical, that the person asking is in some sense trying to

The semantic difference is not small. "Would", using the subjunctive, implies that the "want" is theoretical, that the person asking is in some sense trying to come up with a hypothetical situation that can be written off as being unrealistic or a silly edge case. Using it diminishes the experience of the questioner and is intrinsically disrespectful. The fact that people have got used to hearing it so much that they use it without questioning how rude and unwelcoming it is says more about that community than about the grammar. "Do", in the present tense, does not carry those connotations. It implies "I have acknowledged that your want is present and real, but I need more information about your context to be able to help."