The idea is that it not only measures growth, but measures new customers in relation to churn, with the idea that it's a lot easier to have a long term successful business if you have, say, 1000 new customers and 50 that leave in a month (net 950 new customers) vs. 5000 new customers and 4050 that leave in a month (though also 950 net new customers).
Blue Apron was legendary for its huge churn rate and commensurate high customer acquisition costs. Curious what its quick ratio was, and whether it was just basically ignored.