Scaling back or suspending payroll taxes for a while is simply the fastest way to infuse a cash stimulus into the economy. Even much faster than a stimulus check from the government. Look at how long it took to figure out who got those phase 1 stimulus checks.
By definition it targets American workers proportional to their income level.
Democrats hate it because it passes through the hands of your employer and would bump up your very next paycheck. They want it to look like it's a handout coming from the government.