Google expanded its loyalty features to all merchants, whether they advertise or only use free listings. Through the Merchant API's Loyalty Customer Match Service, you can send Google your members and their tiers directly, without a Google Ads account. Matched members then see their perks, such as member-only prices and shipping benefits, on your product listings.
Repeat customers often search Google before they buy again. If they see their member price on your listing, they stay with you instead of clicking a competitor. Google also says it uses the data to promote your loyalty benefits to potential new customers, so a good programme now works as an acquisition tool too.
There's admin. You need the loyalty add-on switched on in Merchant Center, a Merchant API connection, hashed customer data, an updated privacy policy and consent where the law requires it. Do it once, properly, and it keeps paying.