Mobile apps can be an amazing marketing tool for your business, but they're not for everyone. It wouldn't make sense to have a mobile app if you were a window cleaner for example. I doubt any of your customers would download your app. Hair Salons & Cafe's are more likely to get a lot more downloads.
Sales and customer retention can really sky socket with a custom mobile app for your business, when utilised correctly. It also helps if you already have a large customer base. Some of the amazing features include (digital) Loyalty Cards, Unlimited Push Notifications, Mobile Ordering & so much more.