Creating a mobile or iOS application can offer multitudinous benefits for individuals, businesses, and associations. Here are five key reasons why having a mobile or iOS application is important: 

1. Increased Accessibility:
Mobile applications give users with easy access to your services or content anytime, anywhere. With the widespread use of smartphones, people can engage with your application on the go, enhancing overall accessibility. 

2. Enhanced User Engagement:
A constant mobile or iOS application can give a more immersive and individualized user experience compared to a website. Features such as push notices, in-app messaging, and user-specific customization contribute to advanced levels of user engagement. 

3. Optimized Performance and Speed: 
Mobile applications are designed specifically for the platform, allowing for optimized performance and faster loading times compared to mobile websites. This bettered speed and responsiveness contribute to a positive user experience, as users tend to prefer applications that work seamlessly and fast. 

4. Utilization of Device Features: 
Mobile applications can leverage the unique features of smartphones, similar to GPS, cameras, accelerometers, and more. Integrating these features into your app can enable a wide range of functionalities, giving users with a more dynamic and feature-rich experience that goes beyond what a website can offer. 

5. Brand Presence and Recognition: 
Having a mobile or iOS application contributes to structure and strengthening your brand presence. It serves as a constant memorial of your brand on users' devices, buttressing brand recognition. Additionally, having an app can make your business appear more modern and tech-expensive, potentially attracting a younger and tech-orientated audience. 

In summary, a mobile or iOS application can significantly enhance accessibility, user engagement, performance, and brand presence, making it a costly asset for individuals and businesses looking to establish a strong digital presence and give a flawless user experience.