【UILabel】"set text" is too slow

Question

When setting UILabel.text to a string with many line breaks, it takes too much time.

Why is this?

Is there a solution?

@IBOutlet weak var textArea: UITextView!
@IBOutlet weak var label: UILabel!

@IBAction func tap(_ sender: Any) {
    var longTextWithLineBreaks = "";
    for _ in 0 ..< 50000 {
        longTextWithLineBreaks += "1\n"
    }
    
    var longText = "";
    for _ in 0 ..< 50000 {
        longText += "12"
    }

    //  UITextView
    self.textArea.text = longTextWithLineBreaks;    //  fast
    self.textArea.text = longText;      //  fast
    
    //  UILabel
    self.label.text = longTextWithLineBreaks;    //  too slow!!!!!! why???? processing time has minute over, CPU 100%
    self.label.text = longText;      //  fast ^^
}