Why can't we always use a layer and what is the purpose of a custom UIView?

Using UIView instead of CALayer for user interaction:

• Event Handling: UIView is part of the Responder Chain hierarchy, allowing it to handle user interactions (touches, gestures, etc.). CALayer does not do this directly.
• Hierarchy: UIView builds a view hierarchy, which is higher-level and more intuitive for constructing user interfaces than the layer hierarchy.
• Animations: While CALayer supports Core Animation, UIView provides simpler and higher-level animation mechanisms, such as UIView animate.
• Auto Layout: UIView works with Auto Layout to build adaptive interfaces, whereas CALayer only operates with frames and transformations.
• Accessibility: UIView participates in the accessibility system.
• draw(_:) Method: UIView provides the draw(_:) method for custom drawing, which is managed by the system and easier to use than delegating drawing to a layer.

layer provides lower-level access to graphics primitives and animation but does not offer a full set of features for building interactive user interfaces.