Tomatoes are a vine. Left to themselves they will just sprawl and spread. However, if you've been reading this forum, you will see lots of comments from people with staked up tomatoes about taking the bottom leaves off, to avoid soil born diseases where the leaves touch. And if a tomato (the fruit) sits on the ground, it will almost always rot where it is touching the ground. So it seems like an unstaked tomato would have lots of problems like that. But I've never tried it. You can always do an experiment- leave one wild and cage one and see how they do. We are always learning!
