Why is there a limit of 256 data points for each series for charting in excel ?

Question

Sub chartj()

Dim points, n, i

n = 1000

Dim xtab As Variant

Dim ytab As Variant

ReDim xtab(1 To n)

ReDim ytab(1 To n)

For i = 1 To n

xtab(i) = i

ytab(i) = i

Next i

Charts.Add

ActiveChart.ChartType = xlXYScatter

ActiveChart.SetSourceData Source:=Sheets("Sheet2").Range("F9")

ActiveChart.SeriesCollection.NewSeries





ActiveChart.SeriesCollection(1).XValues = xtab

ActiveChart.SeriesCollection(1).Values = ytab



points = ActiveChart.SeriesCollection(1).points.Count

' only charts 256 data points, not 1000 as expected

End Sub