Here is the issue:
People have a total disconnect between what it actually costs a company to ship something & what they want to pay.
In addition thanks to the marketing lies that some big companies like eBay and Amazon push, people are under the delusion that everything arrives in like 2 days and shipping companies work for free.
UPS, FedEx and most other carriers hugely raised the rates for residential deliveries a couple years ago due to the extra work and driving involved & nobody being home to get the package on the first couple tries. (This is also why Amazon is going to their own gig economy carriers and dedicated Sunday mail delivery contracts)
So, in order to not loose all their residential delivery business to somebody else, UPS, FedEx, DHL etc, offer a cheaper service that takes the package most of the way to the delivery location & then gives it to the post office to go the rest of the way. Generally this results in an extra 1 to 2 business days in transit for the most part (Standard ground packages take 1 to 10 business days depending on sending and receiving location).
Specifically this service is for small packages in the under 10 pounds mostly and generally is used for lower value items or stuff where customers want that "free shipping" lie that makes them feel good. (Nothing in life is free and shipping is NEVER free, you are just paying for it another way not broken out separately on the bill, just the same as the 3% national sales tax you pay on almost everything you buy at the store, that most don't realize is there but is part of the "no credit card surcharges" thing & goes to the credit card companies.)
The little package going to your home address out in the middle of nowhere might cost $15 to $20 to send via UPS ground, FedEx Home Delivery etc, as compared to $9 to $12 with USPS doing the last mile delivery (and just in case you are thinking they should send them all the way with USPS, sending any larger packages all the way with the mail is a fair bit more expensive).
So if you are upset about it, then see if the store you are buying stuff from offers upgraded shipping options, my guess is most people will whine and carry on about shipping time but if presented with a checkout option for $10 (or "free") shipping and $15 to $20 for shipping, they will pick the cheaper option, but still complain.
What can get annoying is when you are not given the option to pay a bit extra for standard ground shipping & only have the USPS/Ground hybrid options or the expensive next day / 2 day air choices.