A SIP mandate is set up once, but the situation it was set up for rarely stays still for years at a stretch -- income changes, a goal date moves closer, or a bank mandate is due for renewal.
A half-yearly review is not about reacting to short-term market movement. It is a fixed checkpoint to revisit the same three questions every time: does the monthly amount still match the goal timeline, has anything changed in income or expenses that should be reflected in the step-up, and are the mandate and nomination details still current.
Nothing is recommended or changed without that conversation happening first against the written goal on file.