The reason for this are the UI5 SDK restrictions concerning supported devices. Currently the following plattforms/devices are supported by the UI5 SDK:
|UI5 Browser Compatibility Matrix|
Maybe this will change in the future, so the latest support information can be found at the SAP Plattform Availability Matrix (PAM) or inside the UI5 SDK Documentation.
The following post will show you, how we handle unsupported browsers to decrease the needs for customer support...