The driver has a 200-250 stop route optimized for efficiency, they attempt delivery when near your house. At 7pm a driver has been on the clock for over 10 hours; this is unlikely to change due to air delivery commitments. Over peak season 14 hour days (DoT limit) is very common, with a 14-hour delivery window it's simply not possible to get everyone's packages to them in the evening.
If it's too high, I assume things like drone delivery will eventually replace deliverymen since they are more likely to not mind working evenings, nights, and weekends.
It's less about the guys, and more about the support infrastructure required for more delivery vehicles (even rented ones via the guys' salaries), insurance, more loading bays to get 7x more vehicles ready, more loading staff (or robots) to load 7x more vehicles, etc.
Honestly, I dread the thought of hundreds or thousands of drones buzzing around the city on a daily basis. It's already pretty bad at many touristic spots because everybody needs their own little aerial video that nobody will ever watch.