Think about online buying in general. Your order arrives, everything is as you expected, why on earth would you leave a review? I don't review Tesco's home delivery every week!
Now suppose something goes badly wrong. You can't wait to get onto Facebook and tell them what you think. And, surprise surprise, most of the customer comments there are from people who have had things go wrong. Of course, because you don't leave a review every time something goes right.
If something goes really badly wrong, you might even seek out online review sites and tell people there what you think.
On ebay where they seem to persuade a relatively high percentage of buyers to leave feedback (probably because the buyers get feedback themselves) a feedback of 98% means "don't touch this seller with a bargepole" doesn't it? The same on Amazon, although on Amazon apparently only about 3% of customers leave feedback ever. But they will if the feedback is bad!
Now think about a tiny business selling unproven items for the first time. Someone is brave enough to try the first one (actually you don't have to be all that brave when it's free returns!) and they like it. Great! Now perhaps that happy customer will leave a review and others will buy.
Only they don't ever leave a review, no matter how much I beg, no matter how many times they promise, because leaving a review takes some effort (especially when you have to wait ages for the reviews to actually load before you can leave one - alas Shopify have no interest in fixing that problem which they are well aware of). So the next person considering that item thinks it's a big risk and won't try it (especially if the teacher has recommended a better known brand).
So this is a plea really. Please be nice to me. If you like your product please leave a product review. I am not asking for Elida Violins reviews (though of course those are always welcome), it's the products that I would really really like to have reviewed. And yes you can be completely honest, I don't censor reviews!