a lot of Android devices do support that - which I’ve found very useful in the past. sadly iOS doesn’t, so although my iPad has a great screen I can’t use a bluetooth (or USB/Lightning) mouse with it … when I’m using the iPad on a stand with a keyboard, I’d prefer a mouse to quickly move the cursor rather than reach forward and tap… also when using Remote Desktop app to control a Windows PC, having a mouse for more granular control would be great. Fingers crossed Apple are listening and iOS 13 will give us that 
