One, if everyone else is dead, they kind of should be to keep it moving and not going back. Especially if it's going into overtime. Nothing makes me more salty than losing games we could win if people contested instead of fearing death more than a loss and just staying around it and only going towards it after we lose, like "oh, guess I should start touching it no-" "NO BITCH IT'S TOO DAMN LATE!!"
In any case, the real, unfortunate tragedy is that 4-out-of-5 times, a Genji running around doing nothing is useless and would be much better as a Tank doing nothing but sitting on the payload. Yes, flankers aren't meant to be on the payload, but that's why flankers are kind of garbage in OW, because it's all about winning teamfights centered around them. Unless they seriously buff a flanker, they'll never be as useful as healers, tanks and real DPS like S76. The complaint of flankers not being on the payload is a sideissue, the larger complaint is that, like Snipers, most people are just bad with them and would be better as a bulkier character on said payload.

I never really got the "GENJI AND TRACER NEED TO BE ON THE PAYLOAD BUT THEY NEVER ARE." meme.

They're flankers, they shouldn't be on the payload.