I dont know why but I buy everything. Even things you can borrow or rent like a coil spring compressor or a ball joint removal tool.
I bought a hand held Porter Cable router to use on one project. And a router bit set. Sitting on a shelf.
I bought a shop press to use on a Camaro bushings. $100 taken apart and put on a shelf to be used again....no idea when.
I have cases and cases of things on the shelves in my storage unit (no garage).
If i can justify it by saying "i need it atleast once" ill buy it.