Teeth should be aligned with the jawbone without gaps. However, teeth rarely grow large after they erupt, so they are designed from the start to fit the size of the jaw.
When a child has a small jaw, small teeth grow in, and as the jaw grows larger, they are replaced by larger teeth that fit the jaw perfectly.
Adults also have a larger number of teeth. Children have a total of 20 teeth, but as they grow out, the back teeth come in and there are usually 32 teeth at the end. Some people do not have wisdom teeth, which are supposed to erupt at the very back, so they usually end up with 28 teeth.
By the time the adult teeth come in, the jaw bone has stopped growing and the jaw will not grow any more, so there is no need to replace the teeth.

Only three types of teeth come in: primary incisors, primary canines, and primary molars, which total 20 teeth (upper, lower, left, and right). The molars do not erupt, but by the time these teeth come in, the jaw bone has already grown enough so that there is no need for them to erupt since they will not grow any further.