Sucker them now, or sucker them later. Each leaf axil will eventually try to grow at least one sucker, and often a second after the first is removed. Since delicate, young leaf is an invitation to aphids, I just remove them entirely, as soon as they're large enough to reach safely. My only real hardship with that approach was applying it to Sacred Cornplanter rustica, which, like most rustica, wants to be a bush.
As to why some begin to sucker early, I really don't know. Some varieties are more prone than others. Some seasons are worse for early suckers than others. If it's something that I am causing--germination conditions, seedling mix, time before transplant, weather at transplant time--I haven't identified it.
Bob