I just recalled the 45 amp figure from conversation with the guy who I'm buying the truck off of or from reading the internet.. could well have been 35 amp. The guy I'm buying off indicated that he had a 35 amp fuse and wasn't having trouble with it blowing.. just that its not meant to keep drawing that high of amps while engaged.
As far as 'why people put them in' I couldn't say. I did look at them when planning my build and wasn't really considering them as they are a bit overkill for what I need and more pricey than i was willing to pay. But given that they come with the truck I'm pretty happy that they are there