The best feature about Simplecart is its ease of use for people who are new to online stores, I just set up my first store in minutes as it comes ready outofthe box! You can also add features like coupons etc but be mindful not too much complexity may make things hard later down time if you're looking at adding additional tools or services yourself (like payment gateways).
We were able solve our checkout flow issues which was really important we wanted an ecommerce platform built upon modern JS practices so this fit well into how most developers these days build their projects - hence why there's no complex integrations required from us either since everything has been integrated nicely with each other already through standardised solutions provided by them such as REST APIs.