Apple Pencil

Because iPad Mini 4 doesn't support Apple Pencil. If you want an iPad which supports Apple Pencil, you need one of the following iPad's:

• iPad Pro, 12.9-inch (2015).
• iPad Pro, 9.7-inch (2016).
• iPad Pro, 10.5-inch (2017).
• iPad Pro, 12.9-inch (2017)
• iPad Pro 11-inch and 12.9-inch 2018
• iPad Pro 11-inch and 12.9-inch 2020
• iPad (2018)
• iPad Air 3 (2019).
• iPad mini 5 (2019).

There are however, alternative electronic stylus you can check out. One of the most recommended is the Adonit Pixel.

Because older iPads made before the 2015, lack a screen hardware layer that is needed in an iPad screen that is needed for an Apple Pencil to interact properly with an iPad screen.

You will need to seek out alternative, third party stylii that are compatible with older iPad models.

Good Luck to You!

Because when iPad 4 Mini was designed, it wasn't designed to work with Apple Pencil. That's all any of us can tell you.