Can't Uber drivers start being drivers or stop being drivers whenever they want on their phone, other then when they are driving someone? Can't they choose whi

Can't Uber drivers start being drivers or stop being drivers whenever they want on their phone, other then when they are driving someone? Can't they choose which customers to take? Using their own cars? Many drivers have 4 apps open at once and then turn off the others when they accept a pickup. Couldn't you just call them lead sourcing companies?