If the EU uses online signature for European Citizen's Initiative, why isn't voting online for elections or policies not allowed?

https://citizens-initiative.europa.eu/_en, This is the initiative I am talking about. You have to prove you are an EU citizen and then you can sign for the initiatives you want and if a million signatures are reaching within a year then it must be brought to the EU commission.

So if citizens of EU member states can sign online, why can't they vote online for elections or referendums? If possible, this would decrease the need and power of representative democracy and move closer to direct democracy, which I argue is a good thing