Let’s say that one day, you receive a package in the post. It has a strange return address you’ve never corresponded with. Inside, there is a small bottle of mysterious liquid with a note attached that simply reads: “Drink me”.
Would you just shrug your shoulders, open the bottle, and guzzle down its contents?
Then why oh why, when people encounter mysterious emails beckoning them to run attachments of executables, they just dumbly click on?
For the average user, there is absolutely no reason to send or receive executable programs or scripts (anything with an EXE, BAT, COM, PIF, VBS, etc. extension) through email.
Executables can be viruses. Especially ones where you cannot guarantee their origins. So use some sense.