Two people have to agree and one of them was not there
A remodel is a household decision, and a proposal delivered to one person becomes a summary relayed to the other.
Kitchen and bathroom projects are almost always joint decisions. Both people live with the result, both care about the money, and their priorities frequently differ.
A consultation with one of them produces a secondhand account of what was said, delivered by somebody who was persuaded, to somebody who was not there and did not choose the contractor.
Requiring both at the design meeting is the obvious answer and it costs appointments. It also raises close rate substantially, and given what a consultation costs in design time, that trade is usually favorable.
How it is asked matters. Framed as making sure nobody has to sit through it twice, and that questions can be answered once, it is accepted easily. Framed as a rule, it reads as an obstacle.
Where it genuinely cannot happen, the material left behind has to carry the argument alone, which means a document the absent person can read and understand without you.