Just going to point out that it's currently peak season for the USPS. Everyone and two of their brothers are shipping or having something shipped this time of year.
Also, money orders are the same as cash. You don't just decide not to sell them because it's a PIA. They're accountable. Honestly, they're not that tough to deal with. Easier than processing a certified letter. A clerk in a post office didn't delay them. That came from a lot higher above them. Of course, you only see the clerk, so it must their fault.