Most projects for a remodel do not require drawings. However, for some projects, it is best to have them so that everyone is on the same page. For kitchen renovations, drawings are a must. Drawings help both the homeowner and the contractor know exactly where everything will go and how the project should look before any work is started.
Bathroom remodels, not so much. Typically, everything stays where it currently is, and we are mainly giving the room a face lift. There are times when major work is done to a bathroom, when fixtures are being relocated, but drawings should not be necessary if you have the right contractor.
However, when you are building an addition, drawings are required. Not only does it help the homeowner and the contractor, local municipalities require drawings so all structural elements are included per local building codes. When in doubt, check with your contractor and he/she should be able to guide you through the process.