A mobile app attracts and keeps customers when it does something a website cannot - working offline, using the camera or sensors, sending notifications people want, or earning a place on the home screen through repeated use. If the app is a wrapper around content someone reads once, a responsive website serves them better and costs a fraction as much. The real question is not whether to build an app, but whether the behaviour you want is habitual.
The test an app has to pass
An app asks a great deal of a customer before it delivers anything. They have to find it in a store, decide to trust it, download it, and give it space on a device they curate. A website asks for a tap on a link.
That gap is the whole decision. An app is worth it when someone will return often enough for the install to amortise - a training programme they follow weekly, a service they book repeatedly, a tool they use at work every day. It is not worth it when the interaction is occasional or one-off, no matter how much better the app experience would be in isolation.
What an app can do that a browser cannot
Offline operation is the clearest case. For Flinders University we built SuspectED, a field-ready app that lets frontline responders detect, document and report biological threats with forensic-grade chain-of-custody. It works fully offline and has been deployed in developing countries including India, Pakistan and Indonesia. No browser-based tool was going to serve people working where connectivity is not assumed.
The others are notifications that arrive without the customer coming to you, deep hardware access such as camera, GPS and sensors, and performance that stays consistent regardless of the connection.
Attraction and retention are different problems
Launch attention is achievable and short-lived. NKO Club drew more than 10,000 members within 24 hours of launch, on auto-scaling infrastructure that held without degrading. Revia reached number 3 in Apple's Health and Fitness category within 48 hours of launch, after a four-month build.
Retention is the harder and more valuable half, and it is a product problem rather than a marketing one. For Fitstop we built the member app and the franchisee operations portal across 100 or more gyms and 50,000 or more active members, lifting user retention by more than 10 percent. That came from what the app does week after week, not from what it did at launch.
Why apps fail to attract anyone
The most common reason is that the app duplicates the website with no additional capability, so there is no reason to install it. Close behind: an onboarding flow that demands account creation before demonstrating any value, notifications that serve the business rather than the customer and get switched off within a week, and a launch treated as an end point rather than the start of a release cadence.
An app that is not being improved is depreciating. Operating systems change underneath it, devices change, and expectations move.
How to decide
Ask how often a customer would genuinely open it in a month. If the honest answer is once or twice, invest in the mobile web experience instead. If it is weekly or more, and there is a hardware or offline capability involved, an app is likely to repay the cost - and the money is better spent on the few things they will do repeatedly than on matching every feature of your website.