This is because architects are not builders and they might tell you or agree with you about a budget only to land the project with you. Then when you put it out to bid you find out that you can’t build it for that budget. That is doing it backwards and it’s call DESIGN-BID
This is why you hire a “design-build” contractor. We will design it, give you a detailed contract in writing and go over everything with you before you sign anything. This way you don’t waste money on doing construction blueprints only to find that you over designed.