Non Zerodha demat being kicked out of trading platform

I have a ISSL demat account linked to trading out.
I received this mail saying that unless I open zerodha demat account, I would no longer be able to use Zerodha platform. All non-zerodha demat accounts would be delinked.
I find this ridiculous being forced to change demat account, for no advantage on my part.

Can check this.