Fed ex ground workers are not unionized, they are independant driver, unlike UPS. Not all fed ex ground drivers drive he same trucks, many own their own trucks, or rent them.
There was good reason for this, but I don't remember, it had something to do with Unions, Fed Ex ground, if combined officially with Fed Ex, there would be problems for some reaon...but that's not important....
BECAUSE the drivers for fed ex GROUND are esentially "on their own", thye do not follow the same schedule one might expect. For instance, if you love in a rural area, the driver might wait until he has a full truckload of packages going to your area before going there, instead of wasting his time going all the way tere for one package--remember, they're on their own time, not the companies, they get paid by deliveries, not hours, so it makes sense to prioratize deliveris. It does suck for rural/remote locations, which in that case, go UPS.
My father's buisness deals with both, getting deliveries and shipping out UPS and fed ex ground. Ups ground, at least here, is horrible on packages, they break things that are packed to surbvive a 10 foot drop...I know, I used to work there...