Why does voting start so early

I just do not understand why voting starts so early for presidential elections. I am currently

 living in South Carolina and the voting started like 2 or 3 weeks before the election and it was

 everyday from morning to evening. If they are going to be starting voting so early then why

 not just hire enough people to go door to door. I believe this would be more secure can

 guarantee that there will be no illegal people voting, this would also make it so that every last

 person who would like to vote gets the chance to vote. The next best part is that they will have

 all the votes counted much faster, there will of course be them people that wait until election

 day to vote but I can bet that it will not be as big of lines as normal. I know I would like it and

 I know it can get does the proof of that is the census. I believe that it would be even better if 

they were to make an online portal that is secured with blockchain technology to do voting at

home. They could require biometrics like facial recognition so that they could verify your 

face with the picture on your ID that proves your citizenship.   

The Right to Vote

Every US Citizen should have the right to vote... I don't think the should banish you from being able to vote because of past criminal actions... It is wrong to do that, why because you can be elected into a political office with a felony... Why should we not allow Felons to vote?? With dumb laws like that shrinks the amount of voters that can and will vote, this country was founded on the power of the people and in my opinion you can't have the power of the people when you tell some they have no right in voting on leaders or even raising taxes in your town... That in my opinion is wrong your telling someone he has no right to voice his opinion with a vote if he doesn't agree with a possible leader or maybe even that new levy your town is trying to get passed... I do agree that in order to be eligible to vote as a felon you should have completed your entire sentence... Voting is a right given to us by the US Constitution don't let the government try and limit our rights that are given to us... If you do what was the sense on the US Revolutionary War...