By default, Planner minimizes the number of kilometers traveled in all your plans. This allows you to achieve more efficient planning considering transport costs, since it allows you to save route time and fuel costs.
In any case, you can modify this configuration and balance the stops between your vehicles. In this way, stops will be assigned to all the drivers of each created plan.
To make this change you must perform the following steps:
Go to Project Settings (gear in the left vertical bar)
Enable Balance Stops
Finish the process by clicking Update.
NOTE: If you want to distribute stops only for a specific plan, visit the following article.