Why should we stop preterm contractions; isn't that my body telling me the baby is ready to come out?

Term is best 4 baby. Preterm labor affect 1/8 of pregnancies making it one of the most common complications of pregnancy. Preterm birth can lead to serious complications. You and your doctor will monitor for signs or preterm labor as part of your routine prenatal care. There are medications to slow or stop labor that can be used if needed and some women qualify for weekly Progesterone shots.
Safety. The bast way to keep a baby healthy is to carry it to term in the incubator that was designed for the purpose. Preterm birth frequently leads to need for oxygen, nicu care, intravenous fluids, antibiotics, brain hemorrhages, etc. If labor can be stopped, every extra day is one more chance to avoid the complications of preterm birth. Bodies respond by reflex, not reasoned thought.
Benefits vs. Risks. Are what the doctors are telling you. Unless your uterus becomes a hostile environment for your fetus because you develop an infection, severe pre-eclampsia or other medical condition, all of which have signs for which your doctor is monitoring you & your fetus, it is best for your pregnancy to continue until your doctor is sure of lung maturity & optimal growth & gestational age.