Building new mobile apps requires basic services, such as user registration, account management and data storage. It takes significant resources to develop each of these for every new app.
Meanwhile all your apps and websites end up different, resulting in a disjointed customer experience.
As your needs grow, you'll want to surface data from back-end applications or cloud services to all your apps and sites.
Because they all exist separately, you'll have to tediously manage each one individually.
Alternatively, starting with the Liferay platform equips you with immediately useful common services. Identity management and data storage can be centralized. Application logic can be reused across all your mobile apps and websites.