I see the option to add nominee in my local crypto exchange, WazirX. But I have not seen such option in international exchanges so far. Any reason why? This can be a good option which will hell transfer of funds to relatives in case of death of main account holder.
Your country's local exchange made this possible as a result of them being active and operating in that locality with some regulatory authority involved, which means the exchange has the required information, both legal and personal, that could be used for transactions or ownership, which many other international exchanges don't care to have.
Let's not forget that centralised exchanges are no different from our local banks, and as such, the exchange can also be following the same monetary policy that is governing the country's financial system, so it's easy for them to do that.
If you are the type that saves money on crypto exchanges, then that might be helpful for you, as you don't need to worry about who will be in charge of your funds if you are unable to reach them, as many people always do, as you will have to set those up on time.
But saving crypto on exchanges is not the best option; they are meant for converting, selling, and buying and should be used for such. 24 hours of holding on exchange is even too much to decide where to withdraw your money.