This is what all loyalty programmes leverage: rewards in exchange for loyalty.
So, why not including something like that into your shop too? It is easy with YITH WooCommerce Points and Rewards, a plugin developed expressly to manage point collections to loyalize your customers.

For each purchase, for each action in your shop, they will collect points that, summed together, will turn into a free gift or a discount on a new purchase.
But for those customers for whom it is almost impossible to reach even the first reward (so, those on which point-based programs have no effect), instant rewarding is the best choice: the immediate gratification that, right because not required, is much more efficient in instilling a positive attitude towards you in customers’ mind, even in a totally unconscious way.

Sales Page:

https://yithemes.com/themes/plugins/yith-woocommerce-points-and-rewards/