There are enough real things to have to keep an eye on. If you want to be free from fear, there's a real simple option- know when you expect to get deliveries so when someone pulls in the driveway with a delivery van you aren't surprised. If you want to be suspicious all the time, just keep on, keeping on. Sure, it would be nice if they wore uniforms an such....but in the end, it's not all about other people's issues. It's about what we can do to solve our own problems.
I have NO IDEA what is coming to my house. Sure, I order a FEW things, but my wife.... Between Amazon, Peapod, and anything that could be delivered by UPS, Fedex, DHS, USPS, local delivery (like florists), or even freaking freight.... There are not enough apps for my phone, and enough push notifications, to cover them all. Sadly, even she is surprised when something shows up (Oh! forget I ordered that). Sigh....
Which is why when a marked vehicle pulls up, I notice but don't worry about it. They can drop the package at the door. But when an UNMARKED random junker pulls up, and some random poorly dressed person hops out... they get my attention. I am expecting a package, not well.... that. I don't need random folks roaming around.
Side note: expecting a UPS delivery eventually. Keep getting emails notifications that the time has changed. But, UPS has it figured out. Tells me the day, pretty close on time, will ALWAYS be the noisy brown truck, and ALWAYS be the brown outfit. For a while, we even had the same guy. He knew me by my heavy Jeep parts...
Now that I think about it... impersonating UPS would totally get me.