A saved worksheet can open with a different context from the one its author used. A bare table name then points at another schema, or a query fails because the active role can't read it. Check your context before changing data. The current context functions return the role, warehouse, database and schema in effect for your session.
Use fully qualified names in a shared report when its sources must stay fixed. Use a schema switch when you deliberately want several short queries against one schema. These are different working habits, and both are useful. A role switch changes permissions; it doesn't change the database or schema for you.