2 considerations. Security and Secrecy.
Security
One of the standard maxims of software development is "Never trust the client computer"
While I may mostly trust my personal system, I really, really do not trust yours.
People without a computer will be funneled to a local neighborhood bank of systems to vote "online". Would you trust those systems? I wouldn't. Not even a little bit.
Secrecy
"If you wish to keep your job, bring me your verified printout that shows you voted for Candidate X"
{Candidate X, of course, is my brother in law who is going to approve the new zoning law which will help me crush my competition)
An election, at whatever level, is far too big a target to allow even a hint of those things happening.
As a software professional who is dead set against the idea, I am not surprised in the least that many others are also dead set against it.