It can take a lot for retailers to get smartphone users to install an app: Being a regular customer isn’t enough incentive. And once an app is installed, poor performance can easily lead to deletion.

A May 2016 survey by Survata for mobile commerce platform provider Branding Brand and found that seven in 10 US iPhone owners said that earning loyalty points for downloading a retailer’s mobile app had influenced them to download it. More than two-thirds of respondents had been induced to download an app by app-only coupons or discounts.

Of all the choices in the survey, iPhone owners were least likely to say they had downloaded a mobile retail app just because they shopped a lot at the retailer—incentives including discounts on their first order were more persuasive.

But downloading an app isn’t the end of the story: If the app doesn’t work properly, that can cause users to delete it.

In fact, 92% of iPhone owners said that they had deleted a retailer’s mobile app was because it crashed or froze. Slowness was also a bigger turnoff than the simple fact of not using the app.

Separate research from comScore looked at the number of mobile retail apps that smartphone owners currently have on their device, and found that overall, shoppers are downloading more retail apps compared to a year prior.

Thirty-seven percent of respondents said they had between at least six retail apps on their smartphone as of April 2016, up 4 percentage points from October 2015.