Because I hate doing construction. It's boring. Also, the screws in the deck wouldn't unscrew, so I had to rip the planks off the deck to replace them, which is bad for my heart.
I wanted to see if anyone ever had one of the tools in the first photo, a B&D Mitremate. My mother gave me this, along with a Workmate, about 40 years ago. For the number of angled cuts I need to make in large planks, this serves me as a Mitre saw. It's not perfectly accurate, but with care you can do a good job.