For normal bread a rest time may be not useful, but there are special purposes when it may be needed.
For example, I make for myself at home a bread that is highly enriched in proteins, by washing the dough before baking, to remove a large part of the starch, up to 75% of it, so that the dough is enriched in gluten (the wheat flour used has a gluten to starch ratio around 1:6, while the bread made thus has a gluten to starch ratio around 2:3).
If a rest time of at least 20 minutes is not inserted between kneading the dough and washing it, the dough is not cohesive enough and the washing detaches not only the starch grains but also gluten fragments, causing a loss of the proteins that are intended to remain in the bread.
It is possible that with a much longer time of kneading the rest time could be omitted, but when the kneading is done manually and you make just one bread for yourself, it is certainly preferable to knead for only a short time, followed by a rest time during which you are free to do other activities.
