Who is part-time responsible for UX / UI in the absence of a specialized specialist?

Question

Layouts and prototypes

The customer wants to create an application with a WEB / mobile client side, he has a general idea, a small budget for the Front-end and Back-end specialist. Which of these two in such a situation will design UX / UI and stipulate the functionality, which in the end.

Answer 1

Front of course

Answer 2

Whoever wants, he will. Who does not want, he will not.
If you are asked to do a job in which you are poorly versed, and they offer little money, will you do something?
Either the customer himself designs, or he will put up with the risks, which will be done within the competence of those who have undertaken the project.