I assume you are speaking about rootstock growth from below the graft - or the ground. They do provide nutrients for the roots to grow - BUT... these will take resources from the scion and eventually overtake the tree. Get rid of them asap

Sure they do. First, are the suckers from above the graft line? If they are below, they are from the rootstock and will take up energy that the tree would normally give to the upper canopy. They could also take over the variety grafted on to the root stock, in a worst case scenario. Second, do you want branching that low? Even if the suckers are from the grafted variety, you might not want a bush but a tree with a trunk.

Might help if you can explain what you mean by 'suckers' and show a pic. Usually suckering refers to sprouts arising from below ground , usually at the base of a tree or sometimes quite a distance from it.

Tomato plant 'suckers' are an entirely different entity though!