I recently had a word with the person working at Deloitte in the Strategy and Operations domain as a consultant. She told me that she didn't give any case interviews for getting the job.
Do we need to give case interviews only when we target management and strategy consulting jobs?
It depends on the company. MBB assess all the candidates with business cases (even for operation, implementation, digital practices).
In almost all consulting companies/roles, you will be required to solve at least one case before the hiring decision is made. The exceptions are internship applications where I know some interns (in MBB) were only asked to take a test and did a 15-20 minute fit interview.
normally you always get cases as part of the interview process in a consulting firm, I would clarify with HR in case you are in doubt.