I can explain. The guy first buys the car he wants and can afford but then discovers that people make additional items for their car that will (hopefully) make the car faster or more "stylish" in their opinion and/or add features that the owner thinks he'll like. I prefer minor performance enhancements to a power train that already has potential to begin with (not like "ricers" that weren't fast to begin with, don't understand THAT at all).
For some, it then can become an addiction and some don't know when to quit before going overboard, sticking way more money into the car than its worth but then too, that becomes a matter of opinion and the owner of the modded car knows very well that he'll never get his money back if he ever wants to sell it.
I have two "modded" mid eighties cars that I've put more money into than they'd resale for BUT I plan to have both cars for another 10 yrs or so anyway and then to me, it's worthwhile. I don't have car payments, they're paid for so I'm still ahead IMO. One's my 745T daily driver, the other's my summer, weekend "toy" street rod which I may never sell.
I still want more "toys" but I need a bigger garage as I don't have spare room now. I really want a mid eighties Porsche 911 turbo carrera and a '63-'67 Stingray 'Vette, among others. Cars like those need no mods either btw.