why don't more Delivery companies do this.

I've worked in admin/IT at a courier company for almost 20 years and most of the time we resisted showing this, even though the technology was there. Driver's almost always have multiple deliveries on board, and you cannot show a recipient the other locations a driver might have to stop at before the recipients location and when we provided the live tracking, this would constantly lead to complaints about when the customer perceived the arrival time should be. As delivery time predictions have improved, we are now more comfortable in showing this kind of tracking, as we can include a progress bar and ETA. However, personally I feel it's outdated now, as we can send a notification, either when you're the next drop or when we estimate the driver is X minutes away - I prefer that over watching a map.