People are using reviews to make buying decisions
Your online reputation is something Google can’t take away from you. If done right, with online reviews, testimonials, or people saying positive things about your business, then it is surely one of the few things that Google can’t touch. Even if your site gets punished by an algorithm update – you still have an online reputation for customer to find you.
If you have reviews, you will get more clicks than your competitors do. Those clicks & behavioral signals will also benefit your rankings by moving them up slowly but surely over time.